From the recently shown avatar image of the Diablo 3 Fallen Shaman, I cranked out a quick little sketch of one a bit more detailed and accessorized. Tried to make him looking sinister with a tattered mantle. Might work a bit more on it in the future.
If your going for sinister might I suggest you go for a little less of a happy smile and more of a smirk and make the horns less upturned and friendly and a little more traditional demonic. It really depends what your going for though, what you have probably looks closer to the in-game image than what I would do. 1 minute paint over to give some idea, basically making the shape with harder corners to try and remove the rounder cuddly look. Please don't be offended, not intended as as an insult or anything, just trying to help I guess, totally up to you how your artwork looks of course!