Pentomino + Tertomino (5+4 block) Tetris works quite well. I do think it's a bit iffy to have the game go to game over if your time runs out. Firstly, because there's really no feedback that you're about to lose, so then the Game Over screen shows up, and you're like, what? Maybe you could've just dropped all the blocks that were left in that level wherever the player was currently, rather than instantly making the player lose.
I got to level 14.