www.t205resource.com used to have a list of card + back combos, but that site is not accessible right now.
You can see a version from a few years ago at
https://web.archive.org/web/20150906...stsmaster.html
Though there are a few combos that have been discovered since then, that list covers the great majority of them.
This thread also has some great information:
http://www.net54baseball.com/showthr...230355&page=10