Maybe just something implemented directly into the game? A player statistics page, which you could take screenshots of for friends/forums etc.
The only thing is that some statistics would be all time, and some couldn't be. Having the win/loss would easily be all-time, since Zanz already has that stat, but unless he already has a stat/variable that keeps track of wins/losses against specific AI/players, that would have to be implemented, and stats like that would have a clean slate.
Card value sounds like a really cool idea, btw. Also either showing how many of each rare you own, or just how many altogether.