Virginie Quesnay sent me some new icons for Bookcase. I like them so much, I'm going to incorporate them as the default icons for the next release. Since Bookcase will have a new name, the new icons will be appropriate. Although more than just book collections are supported, I like the idea of tying the icon to the original function of the software - namely, tracking a book collection.
Now I just need to make sure I'm installing the mimetype icon properly.
Oh, and Virginie's icons fit into the Nuvola icon theme rather nicely.