It would be great if the cards could hold some sort of value to make them desirable.. embedded bitcoins or a guarantee to reclaim them for btc, haven't found a good idea for this yet.
I think the most likely way this would work is forum users push the creation of their own card, they organise/pay for artwork, they write the characters back story and character traits (based on themselves i guess), they choose how valuable/rare the card is, and then we have a standard process to get the card made up and packaged to fit the other cards in the set.
Not sure if there needs to be a playable game portion to it though (like Magic), perhaps something simple like if you have a hand that trumps another collector, the loser pays for your lunch or bitcoin conference entry or something
Looks like a sweet idea and I'm definitely behind it, with or without a card of my own. I think it will be a neat way to physically document the digital world of bitcoin. My only request as of now, round edges. I think that what makes a trading card, a good trading card. Also lessens the wear and tear. 
