I've poured over many many behind the scenes pictures from the original movie and would like to mirror the original backdrops in a way that doesn't require copyrighted material.
From what i see, the backdrops were fairly generic (rolling hills, dark skies, trees behind a fence...) But when they added the actual set in front of it, it gave the proper depth. I think that would work for WOZ too. There is just enough in munchkin land that rolling hills behind it would add depth. There are just enough trees in the apple orchard that a dark sky and distant apple trees would set them off.
From a Photoshop perspective, I'm capable but not an expert -- so I'll definitely keep you in mind should the need arise. The only thing I'm somewhat unsure of is proper sizing (for layout and cutting). I'm sure some trial and error will be required, but if there existed a blank template for initial sizing, I figured I'd start there.