Sniper Elite 3 was released on Steam with trading card support on 27 June 2014. There are 9 cards in the series, and you'll receive 5 cards at random for purchasing and playing the game.
The other games in the series, Sniper Elite, Sniper Elite V2 (and its remaster), Sniper Elite 4 and Sniper Elite 5 also has trading card support.
Trading Cards
Foil Cards
Badges
Booster Pack
Emoticons
Profile Backgrounds