A few mode ideas have been discussed on the Mailing List.
Competition mode - 2 or more players race to finish levels
Showing both players at once (e.g., split-screen (or on multiple computers))
Might be able to bump other player off the screen in competition mode...
Versus mode - One player plays Tux, one plays Nolok (or other characters) and try to get each other.
Turn mode - Players take turns, when they die it is the other players turn.
I can see two ways to do this:
Michael Lubker (zratchet), who helped with some of the original Milestone 2/onward concepts, is working on designing Super Tux Smash, a multiplayer mod.
Category:Design