Here's a bunch of features listed. Go through this list and think critically which of these you should and could include into your game!
What could we add to the basic Tetris or to our Tetris? A lot.
Achievements, leaderboard, city building metagame, storyline and much more.
Play game and use Tetris as the bases, add the features to a basic Tetris and with every new piece, think how it would fit the game.