Maps with 3 or more teams
I just thought it might be interesting to have a map where there are creeps coming from more then one team at each other.
One idea of mine is a map with four corners where creeps go along the sides of the map directly to their nearest neighboring enemies, and then another stream of creeps that go directly accross the map to the opposite corner's team but there's fighting between every team's creeps in the middle.
Something like this:

An alternate form of this is that there is a height factor so in the middle 1/4 path goes over the 2/3 path and they don't meet at all as there could be a lot of problems with creeps meeting in the middle.