After reading a post about 2v2v2 and so forth the thought came to my head....Free for all maps.  

Each player has a base and thier own stream of creeps which divides up and seeks to conquer, or possibly have it be a situation where you'd have streams of units attacking both opponents to your left and right...and once you conquer them your creeps can go straight across the map to your opponent/through the other bases.

I just happen to think a mode where you can join and stand on your own could be extremely fun for when you have no friends playing online or when you just want a bit of hectic action without being tied to other players.

This also brings to mind the idea that you could have more than one base/teams in maps such as these, or even forward outposts that spawn troops that aren't controlled simply by flags.