My wife (It's her Kindle!) is a digital artist and I have been thinking about processing some images to load on hers. The only downside is that one would temporarily lose the standard images, which we have not tired of yet (I know they can be restored). It would be nice if one could create individual "book covers" for individual ebooks that would come up each time you selected that book.
I have been reading through Manuel Burgos' "Graphics on the Kindle" and following this thread so we'll see.
Perhaps I'll have my own Kindle soon to experiment on.