needs bigger pics...buuuuuut....

Easy:

1. B.E.A.S.T
2. Ripper evo
3. Pillow-Torque
4. Terrorhurtz
5. Chomp-a-lot
6. Megga-mouse

Med

1. Block of Wood
2. ???? not sure...
3. ???? see above :P
4. Pug
5. 44 Toon
6. Behemoth

Difficult

1. Maelstrom
2. Thor
3. Wedgie
4. Whirlpool
5. Annihilation
6. Apocalypse?

Very Hard

1. Tilly evo
2. - micro mute?
3. - erm...dunno :P