Can't see why not.
We have a unifying concept which, if memory serves, is to have each character based around one of the animals in the Chinese Zodiac (or, rather, some element that they represent). Dragon and Monkey are taken.
(I was in a game that went belly up, but there we were supposed to base our characters on cards out of the Major Arcana. There was some confusion because the title of the card does not necessarily represent the area of interest! The Death card, for example, does not mean death...anyway, it was a cool idea, and I suggested it to Ajoxer and Circ when we first considered this game.)