The doors themselves are all traditionally painted with Guoache. Then for some reason I can't remember, I added some quick photoshopped backgrounds. I think I just did the doors initially and then was asked to add the backgrounds, and for the sake of expediency did it in Photoshop.
Some time later, one of the other artists at RedEye took the green door I had done and created the clip below to show how it might be animated.
All images Copyright Red Eye Animation.