It depends on what you are doing with the picture. If you are posting a picture of the awesome hand you drew and slaughtered your opponent with, it seems the same as posting a screenshot of a game. If you are trying to settle a rules quibble, that would be like posting a capture of a rulebook. If you are posting to show the art on the card, that seems like posting a copywritten picture.

I'll leave it to a mod to tell you which, if any of those are okay.