Disney Epic Mickey was recently released on the Nintendo Wii. The project was led by Warren Spector, one of the industry's most respected creators who also happens to be a huge Disney fanatic and collector.
The final result was a strange and unique take on the Disney universe. The concept art is something to behold although I have the a feeling that it might be a bit more apocalyptic than the final game.
Now that the game is out, artists are probably a bit more comfortable posting concept artwork they did for the game. They first I've seen is Sam Nielson's super-cool Prototype Pete.
Hopefully more artists will follow suit, because I'm sure there's a library of amazing stuff waiting to be seen.
Here's one more to grow on.
EDIT: A bit more has trickled out! Enjoy!
A couple from Billy George.
And something by A.J. Trahan, who also did some storyboard concepts.