When obtaining art assets for books in the roleplaying industry, I have noticed there is a lot of input into getting the interior artwork and cover artwork. With selling pdfs (and other electronic editions) through places like DriveThruRPG, you’ll find that those files have the front cover, the back cover, and the interior. They are usually in that order so you can view the pdf as a two-up document with a separate page for the front cover, preserving the page spreads in the printed work. What seems to be forgotten — or at least not considered fully — is the treatment for the spine of the book. I find this odd, because at a store, your book is more likely to be shelved spine-out.
I hadn’t really noticed this until I developed the cover for Magpie Games’ Urban Shadows. For that book’s cover, we only had the front artwork which was to be placed on a black background. The back artwork was a composite of four of the character types, combined specifically for that space. We used an interesting typeface for the logo (and some chapter headings) with a white fill at about 85% opacity, re-purposing it for the spine. I wanted to make it big, bleeding over the edge of the printed spine. As a happy accident, this wound up looking amazing on bookshelves.