Jesus, you guys are blowing me away with your rapid responses. I was expecting a few days of hemming and hawing.
So, uh, here's a link to the full-sized version:
http://img576.imageshack.us/img576/2564/coverart.jpg
And so I don't wind up with pink cows, here's a run-down of what things are:
Background: It's a book. It should be book colors.
From left to right:
Lizard thing: A slaad, can be any color you want as long as it's unnatural and interesting.
Minotaur: Probably some shade of brown.
Rock thing: A golem. Should be rock colors.
Snake/dragon/long-necked thing: A behir. Electric-blue.
Dragon man: A draconian. Silver, bronze, brass, or copper scales.
Ugly dude: Hobgoblin. Should be
this sort of dull orange/red color.
Face: A goblin face (also the villain of the campaign). Should be goblin colors.
What are 'book colors', 'goblin colors', 'rock colors', etc? I leave that in your hands, you artistic people!
Keep being awesome, you guys!
EDIT: Also figured I'd mention that the big version of the image is really goddamn big. The final piece will be resized and cropped to 11x8.5 inches, so do with that what you will. Odds are that means you can resize it, but I don't know much about art, and even less about digital art. So do what makes sense to you!