Gameplay wise and setting wise:
Small or big?
Water?
Open or with chokes?
Night or day?
Summer or winter?
With or without a lot of houses?
I want to make the maps you want to play!

Also I've been wondering, will anyone ever play matches on custom maps? In sc2 basically all the maps are player made. But since the world builder is pretty new I don't have an idea of how much the player made maps will be used.