I wanted to have a wallpaper that would make me "want" to read a book. Not that I find myself not wanting to read on the eReader but still, a nice "cozy" wallpaper makes it more enjoyable to pick up the eReader and start reading.
Since I typically enjoy drinking coffee while reading a book, I used Google Images to look for "book coffee" or something similar and one of the pictures that came up, I threw in Pixelator to more or less frame it. It looks very nice in B/W on my PRS-650.