okay here are a few
-hadies
-will of the wind
-arm of the shadow
-fire cracker
-master of the cave
-barroness of badness
-iron agressor
-agressive acrobat

Awesome suggestions man, 2 of them are in the game now, please let me know if you have any more ideas & i'll write them down :D

I'll give you a few names

-Time Stoper
-Dark Knight
-Psychic
-Crazed Killer
-Gladiator
-Military
-Duelist
-Samurai
-Crosbow Man
-Lancer
-Pistoleer
-Rifle Man
-Lightning Demi-God
-Skeletal Pistoleer
-Hell Hound (Maybe a werewolf-like creature?)
-Werewolf
-Vampire
-Undead
-Fiery Jester
-Master of Cards/Master of Luck
-Merman(Oposite sex of the mermaid, maybe you could do an easter egg set for him to look like aquaman?)

There, i'll give you more ideas when i get, more ideas, for now thats it, i'm sorry if they're too ridiculous, i'll give you all the suport i can afford.

You should have a perk system
It would further influence the game to your liking.