I decided that the green cover would look good if there were blue stamps over it.  I have a large collection of commercial rubber stamps that are so varied (and copyright free) that I sometimes use them despite my aversion to using others’ art in my collage.  Of course, once I’d inked up the glass (with acrylic mixed with gel retarder), it made sense to do a few more stamps.  And then I changed the hue slightly, by adding more paint. And then I stamped some more. And then I changed the hue to a more purplish one. 

For my next stage, I need focal pieces on the covers, preferably something with texture so the book’s owner can fiddle with it.  I was going to try to make epoxy stickers, by dropping epoxy on magazines or other 2-d art, then cutting around them.  Unfortunately, I got casting resin instead of epoxy, and I don’t know if it will work or not.  As with most of these projects, it will probably make the most sense to create a hundred times what I need, select the best one for this project, and store the others to use later.