The masked people

This a painting about my 3 favourite open-world video games. on the left you can see an ork from skyrim with the volsung mask, in the middle a character from borderlands, and on the rigth this is a ranger from Fallout New vegas. But I have a problem : I don't know what to do in the background. Do you have any ideas, please tell me, all ideas are welcome. For now I did simple colored background, waiting for a good idea ... XD