As far as I know, typically the Ace of Spades, Joker, and back design of cards are copyrighted because those are the really unique aspects of a card set. Face cards are often not copyrighted, unless they're clearly different/unique/custom. If you're using a standard deck, you should be fine as long as you don't show those few cards that are copyrighted. If you show the back of a card, it has to be your own design or a design that you have rights to use.