I know you don't want cookie cutter but different background colors can really make a difference. The 2 I showed are not that different but they are different. If you submit back to back days you'll want more of a difference.
Mixing the text up between the thumbs can help make it look different too. Then you can do other things too like I did with this gallery:
http://www.allthepornstars.com/juliabond/sleazy.html