Compete against other players by purchasing biters to fight on neutral ground on your behalf.
Large total conversion mods.
How do I change the number of rounds to make games last longer?
At the moment, you have to edit the config.lua file, the "game_length" variable is what you are looking for.
I haven't had much time over the past year to work on mods, but I may try to move these into the game itself somehow.