One of the relics that Lara finds is a wooden game which looks familiar to her. It's probably an imaginary predecessor of Tetris, given that the designer of Tetris was Russian Alexey Pajitnov, and Rise of The Tomb Raider takes place mostly in Russia.
There are playing cards in one of the rooms at the Gulag. I guess the mercenaries had to find ways to make it through the long cold days in the russian mountains.