My thumbnails are always barren. I purposely leave out as much drawing detail as I can so that I can achieve the most spontaneity and richness in the designs when I actually sit down and draw them, rather than just trying to copy already tight thumbnail sketches. Most of what I try to accomplish with a thumbnail is the pacing of how the words are said and slight compositional ideas.
Believe it or not, this is the only preparation I take before I sit down to compose a comic of this simplicity. For more complex things, I might do a little more planning, but I like the Eskimo Amy comics to feel free and spontaneous.
Here are the thumbnails for the last three comics, they were all done on one piece of xerox paper.
