why not something more Asian in flavour rather than the usual Greek/Roman mythical creatures? maybe a shape-shifting fox (one of the bad bosses, derived from japanese mythology), snake den (gotta love that snake pit in DD), imps (Malaysian one that is <img src="/ubbthreads/images/graemlins/biggrin.gif" alt="" /> ) that can steal & put curses on u but no physical damage which can also be familiars of some bosses u'll encounter, demons from the seven layers of hell (Chinese Taoist folklore) that normally target different sins (a bit like the biblical 7 sins), warrior assasins (can be dressed up as ninjas) of 5 elements, etc.
i will think of some more.
in fact, i just came up with an idea of a kind of mage specialising in curses, some sort of a hybrid of necromancer as well. well it's based a lot on witch doctor lore here in south east Asia. it would involve NPCs, & items found in the game world to create certain curses or potions & such.
will write more on this. <img src="/ubbthreads/images/graemlins/smile.gif" alt="" />