BB1: The Stronghold
1) You'll easily find a place where lays a shotgun surrouded by hedge. Go around the hedge to the corner, there's a small metal door. Open it, ride up with lift. There's a lot of promixity bombs on the boxes. You see garden tools hanging on the wall? Pull the pruning shears and one box in the corner slides down. Contains: Full armour

2) The napalm launcher resides in the castle, find your way to the room with many doors and peek around. After arming yourself with napalm launcher, push the grate just at your eyelevel. It will reveal a secret as long as you can call anything as a secret place in Bloodbath levels. Contains: Invisiblity cloak

3) Find the place where is C-shaped wall which rotates around. Go in and arm yourself with Tesla Cannon. Also, if you look from the door to the end wall, at your left is a carved wall. It will slide down if you stick your greedy fingers on it. Contains: Boots of Jumping

4) There's a life seed in very visible spot. A hedge surrounds it. If you take a look from the tunnel, the left end of the hedge seems to have differently coloured stripe. After a peek, you will find a hidden button, which lowers stone pillar. You can also take a ride up to the life leach because pillar rises again up, but it's somewhat long process so be aware of adversaries. Also you can use Boots of Jumping to get life seed, of course. Thanks for Ryan Turan for information about hidden button. Contains: Life seed

5) Up in the castle is a room with shotgun and hair spray can on the table: window gives a view down to the courtyard. Near the table is wall closet. Open it. Contains: Full armour

6) There's a grave with a starting spot in it. If you walk in the grave a niche slides open on nearby wall. Contains: Voodoo doll

7) Pissed off for all those Tesla Cannon wielding guys? Well, just opposite the Tesla Cannon (inside the C-shaped wall) is another secret place. See the windows up there? Burn or blow up bushes near the stone wall opposite the C-shaped rotating wall. Now, search the wall carefully and you should notice a secret door with a lift. For 'sniping', I recommended Alt-Fire... Contains: Flare gun, a crystal ball

8) There's another path leading to the Tesla Cannon. Go through the large pair doors. There's a brown altar at far corner. Push it. Contains: Tommy gun
BB2: Winter Wonderland
1) Icy waters flow in pool located at the courtyard. Dive in. Contains: Tesla Cannon, several charges

2) In the tower there's living quarters. Although you can open cabins and closets and find spirit armor behind curtain, you can find something even behind clock. Contains: Trigger bomb

3) Another room in the tower gives a view over smaller courtyard. See a small glass window in the corner? Break the glass and jump to the ledge going around the courtyard. Contains: Napalm launcher

4) If you continue your way from the tower, there's a ledge going around the courtyard with the castle's wall. Walk around until you come to the point where wall separates smaller courtyard and larger courtyard with lake. If you look closely there's a mark in wall, just for blowing it up. Contains: Guns Akimbo

5) Yet more comes. Continue your way to the ledge's end (end of path). Look closely at opposite wall. There's a damn small ledge (one-way door... note). Try to jump on it. It won't be easy task, but still doable. If you won't make it, try another way described later. If you get on the ledge, turn around and you see a blazing fire and your prize. Contains: Life seed

6) There's a garden and fountain near castle's main entrance. Walk around the hedge until you find a differently coloured spot. Push it and it will make nice elevator. You can go up and jump to the secret items hidden over tunnel with bushes as a ceiling. Notice the secret door leading to the life seed and a ledge over courtyard at the left corner. Contains: TNT box, a box of flares, doctor's bag

7) Inside the castle there's a living room. Jump behind the couch and crouch. See the switch? Pull it and you hear when something opens in the nearby corridor leading in the next room (with window out to the courtyard). Contains: Full armour

8) You go inside the castle from the main entrance. Just before the lift search the wall at your right. From here you can easily snipe or blow up other players until they also discover this place. Contains: Good sniping place, Voodoo doll

 9) In the castle, there's a tommy gun on the floor. Grab it and look up. Move a little around if you won't see a button. It's shootable, it will activate a lift which rises up and you gain access to the secret room. Contains: Fast passage to the ledge, some misc. stuff
BB3: Bodies
There aren't not much to mention. Elevator lies in the large area down below. Guns Akimbo and promixity bombs reside where elevator goes. The clicking noise which is heard when you climb the stairs is probably a warning sound for other players down, I don't invent any other reason for it.
BB4: The Tower
There aren't much 'secrets' around. You can use buttons around mainly to drop your enemies down, if you wonder that. A window opposite the tower is accessible behind the block, lift leads you up and voodoo doll resides here. Just very opposite this spot is a holding place for life leach and life seed, just walk stairway up, cross the bridge and walk on so you finally reach the place. There's a riding block to the hole other side, it comes like a dog to you when you push the button.
BB5: Click!
1) Largest room in this place contains a tommy gun and a button. In the next room is a shotgun. If you search around, you notice that wall located in the right before the corridor is differently colored. Well, press quickly the button and run like hell in the room containing a shotgun and try to catch the lift. You can jump from here to promixity bombs located in the middle. Contains: Life leech, life seed, several TNT bundles

2) You find a voodoo doll and doctor's bag in one room. Continue your way down the ramp and you probably notice different wall ahead. It's a lift. You get nicely to the promixity bombs up there and, as usually, surprise some dumbhead mining places down there. Four barrels at a time from your shotgun will drop this sucker to there where he/she belong. Contains: Guns Akimbo, full armour

3) There's six promixity bombs near the window in very findable spot. If you come from the elevator, get the bombs and continue your way. Turn to the left but instead going to the ledge and small corridor containing napalm cannon and charges, push the wall ahead. It will slide down. You can get to the promixity bombs here with a little jump and to the life leach with a larger one. Contains: 3x4 shotgun shells, promixity bombs

4) Back to the circular elevator and six promixity bombs. Start from the promixity bombs, walk past the elevator, go to the corridor containing gas canisters and turn at the corner. There's a shotgun beyond the corner, well, take it. Now look out through the window and move your sight to the right and slightly down. There's a ledge above door. Contains: Invisiblity cloak
BB6: Twin Fortress
This is perhaps the greatest map in the Blood to spread envy, anger and frustration among the multiplayer buddies in 4 against 4 team Blood. And vast amount of machine gun bullets guarantee the total exctasy in the rows of weak-hearted enemies. There also aren't much secrets around. You can lock the storage doors and open the flag room from the control center. Most switches release fireballs or bullets flying around the battlefield until they run dry or weapons break. The muddy hellhole in the center is filled with mines. Perhaps there lie only one 'secret' thing, just visible, but somewhat tricky to reach.

1) Use the lift near control center and go up. Choose left way. Walk to the terrace and near the edge. Face wall and jump up a bit. You saw it? Push the wall at the front of you to lower it. You'll get your hands to the life leech.
BB7: Midgard
1) There's a button in room where you can go with elevator. Press it and very quickly get to the opposite side. You just barely can jump on the rising lift. Note: shoot barrels on the lift first or you could get unpleasant surprise when you're taking ride. Contains: Full armour

2) A bridge crosses the courtyard. A button will lower it and in another end is a niche filled with stuff and barrels. Sometimes brigde won't go back up and hangs, so this 'secret' is easily accessible. Contains: Promixity bombs, boxes of TNT
BB8: Fun with heads
Again, there aren't much secrets. In another auditorium resides a napalm cannon and few gas canisters and in another lies a voodoo doll. In the shower are a full armour and promixity bombs. Doing a goal with a head won't score a point, even there is a scoring board around (if you know why, let me know, I tested this only with single player deathmatch by executing my Network.ini containing those rows from Blood help file). And again we reach the finish line. Have a nice bath, I'm now finished with this thing. Hopefully you enjoyed screenshots.
BB9: Monolith Building II
1) Near the Christmas tree are two doors. Blow open the one on your left. Contains: Life Seed

2) Jump behind the Garbage Can next to the stairs. Contains: Guns Akimbo

3) Upstairs, enter into the only unlocked door. Now blow up the wall behind the TNT bundles. Contains: Life Leech

4) In the room with "Decoy" on the computer screen. Blow the wall to the left of the computer screen. Contains: Proximity Detonators, some Shotgun Shells

 5) As you leave the "Decoy" room, turn to your right. Walk down the hall until you reach the light switch (it's on the right side of the hall). Blow up the wall to the right of the switch. Contains: ???
BB10: Power!
Nothing much that isn't obvious. Although you might miss the lift in the room with the three lighted alcoves. Take it up for a few supplies
BB11: Area 15
You should be able to find everything very easily. This is an extremely straight forward Blood Bath arena.
CPBB1: Crypt of Despair
1) As you enter the crypt from one side, blow up the crack in the first tomb to your right. Contains: Fire Armor, Trapped Souls

2) As you exit the crypt from the other side, blow up the wall to your right. Contains: Life Leech, Box of Shotgun Shells
CPBB2: Pits of Blood
1) In the control room above the spinning blades, push the switch. A smasher will turn on, allowing you to gain access to the underwater area under the spinning blades. Contains: Tesla Cannon

 2) When you're going up the ramps around the small pool of water, you'll find a switch. Hit it, and jump into the small pool. A wall will be open revealing some supplies. Contains: Tesla Cannon, Batteries

3) When you find the switch which raises and lowers the bars, enter into that room. On the other side of the small counter, you'll see an odd panel. Push it. Contains: Tommy Gun
CPBB3: Unholy Cathedral
Another straight forward Blood Bath arena. Only a couple of things might not be too obvious. There's a switch outside which lowers the wall under the window. And there's a door which doesn't look like a door at the end of a small hall. Other than that, you should have no problems.
CPBB4: Deadly Inspirations
In the center of the map, you'll find lots of goodies behind curtains, and underwater. Be sure to explore this area thoroughly. Nothing is really hidden.