This game works the same way as "Make the Card", except you are making the card based off of artwork alone.
So if someone posts this art:
I can make a card with a part of this artwork within it, like this:
After you make your card, you can find another piece of artwork for someone to design their card around (preferably WoW related). If it's necessary, you might also want to post a link to where you got the artwork if it will help someone get a better idea of what is in it.