I think they should be made by a single person so you don't have a billion clashing styles and no AA becuase they don't know how.
Make cards add up to total points, like colour based on rareness.
Maybe green would be the most common (GreenBH)
Yellow for next (Cheese)
And I dunno after then.
Oh, and people can request their own card to be made, as long as the person has their avatar to make it.