I'm not saying to do it exactly like this, but to me, this is what it SHOULD be.
Every player interested in making their card can, but they use a base template (like the one Demian provided).
So each card will have a picture of you, your ID, a description, and rarity (Bronze = Common, Silver = Uncommon, Gold = Rare)
It will be just like collecting, no battles or stuff like that.
When you get a card, there should be a GUI that allows you to view it.
You are able to trade it.
IT WORKS JUST LIKE THE FRIKKIN HAT MOD, ALL YOU CAN DO DIFFERENTLY IS TRADE THEM!