I use a mix of stuff...paper, plastic & metal minis get used alongside styrofoam, plastic and other surroundings.
I own a lot of Dwarven Forge, but only use it for BIG battles and/or minis combat games. Usually, its just the battlemat and ink.
However, I also use a lot of stuff I find in hobby stores- they're full of things like trees, hills, etc. for the train hobbyists, dioramists and the like. Water? I bought some sheer blue fabric to drape on the battlemat.