[....]I had some ideas:
When player (worm) dies, you could make the death -game over- more spectacular.
Maybe the worm could explode in a rain of blood, or you could make an animated scene of the death with the worm going in bloody pieces.
The nature of the worm makes me think this will not be an hard work for you.
Alternative game modes.
-Two worms can fight one against another. In the surface, worms can take power-ups, and avoid mines.
-Soccer (calcio) mode. two players 1Vs1. The worms must push a big rock doing a goal into the goalposts.
*Single player "Good Side" Mode
-you move people, and must shoot worm. Worm movement is "Artificial Intelligence based". Could be good to move more people together, in a "Cannon Fodder Like" control system.
Those game modes are pretty complex, I hope my ideas are good for this game...or maybe for its SEQUEL