For games that include many different decks, the ability to draw random cards, and to search for specific cards, in one deck and then insert those cards into another deck would be very useful. As well as being able to include or exclude individual cards from a deck for a specific session.
Also, for games in which some cards are displayed face up in a player's area and others are in their hand, it would be nice to be able to manipulate one of the "hands" a player has above his or her video/portrait, by resizing, rotating, and moving cards, to create a customizable player area that is visible to all players.