I didn't meant the background but the land they sit on, so for sand(units in desert regions) or snow(sweboz rulzzz) footprints can be noticed or rocks will be present in some of these scenes and neat things like this.
So the grounds now are 3D instead a simple plane like it was in the past or in some cases just a pic was used and the unit was placed on top of it, here's a pic to give a general idea(mesh only the rest is a surprise:P):
https://img505.imageshack.us/img505/1033/34248161.jpg
However specific faction backgrounds can be added but we haven't checked how it will look.