My main criticism is the lack of elves. What made you leave elves out of this illustration? Are you perhaps prejudiced against them? Are you an elf racist? I think that may be true...
But seriously, the color in this is great, so great that it almost distracts you away from the fact that the drawing is so solid. I love all the detail on the Witch Doctor and the creature in the background is really dynamic.
My only complaint is that I think the creature in the background on the right lessens the impact of the central image. If it was just the Witch Doctor, I think this would be a knockout. The creature in the back is so well-done and interesting-looking that you should give him his own illustration (!) And that fiery orange background would be a great contrast to the blue glow of the witch doctor's left hand.
Submitting to a Blizzard competition is tough -- they must get a million entries. Hope you did well.
Jim