Decks of cards will definitely be added in the future. Many games you suggested are trademarked, and therefore wouldn't be implmented directly, but we were planning on a Uno spinoff. Go and (Chinese) checkers should be trivial to add.
Regarding Dungeons and Dragons, I was thinking about 1 page RPGs (example: Lasers and Feelings). These often have licenses compatible with our game, often allowing to be directly used or modified as long as the original author is acknowledged. These games would fit the SS13/SS14 round format better, as they take little setup, and it would not be a massive loss if you get blown up while playing (unlike DnD).
Hangman, Tic-Tac-Toe and other drawing games would probably be better if we had some kind of "paper and pens" implemented, and then players can just play them on the go (assuming we can trust players with drawing stuff ).
Dunno about Four in a Row, would require quite some extra coding and spriting to fit the top down perspective is difficult, but I suppose it could be done.