Well i liked it, but..
.. you should add lives. At a certain point the ball went so fast, all i could do was stay at the left corner to catch the first ball so it took some time before my score went down, and in the meanwhile grab the blocks with the snake-head. And that even gained me points.
I think you should make that part less hard (so you still cán play both games in one) and give us lives that decrease when you fail to catch the ball instead of points decreasing (so you still háve to play both games in one).
Other than that, nothing is really needed. Better graphics and sounds would be nice, but not needed too much. As for giving the snake penalties for hitting the wall and making his body grow: why would you? the game is fine the way it is. It isn't supposed to be the exact both games, is it? Besides, that would just make it too hard. You should make it so that you have to survive with pong, and see chances to increase your score with snake.
Just my two cents though. Nice game. Peace.