Strike Suit Zero had Steam trading card support added on 20 July 2013. There are 5 cards in the series, and you'll receive 3 cards at random for purchasing and playing the game.
Strike Suit Zero: Director's Cut is an enhanced version of the game, and also has Steam trading cards, but a different set. You won't receive this game's cards by buying the Director's Cut, or vice versa. Strike Suit Infinity also has trading card support.