Sniper Elite: Nazi Zombie Army had Steam trading card support added on 13 July 2013. There are 8 cards in the series, and you'll receive 4 cards at random for purchasing and playing the game.
This game's sequel, Sniper Elite: Nazi Zombie Army 2 also features Steam trading card support.
Trading Cards
Foil Cards
Badges
Booster Pack
Emoticons
Profile Backgrounds