Riptide GP2 had Steam trading card support added on 7 March 2014. There are 10 cards in the series, and you'll receive 5 cards at random for purchasing and playing the game.
Riptide GP2 - Churn Alley (female)
Riptide GP2 - Stadium (male)
Riptide GP2 - Lancer Schematic
Riptide GP2 - Scprpion Schematic