It could just be a matte painting projected from behind a curved screen since i dont see any shadows. There are quite a few pictures of this set that show the whole background. I think you see this same screen when luke is forced out of the window.
To recreate this in 1/6th, I've been wondering if taking white plastic and applying a decal of this background, then lighting it from behind would work? You may need 2 sheets of white plastic if you want LED lighting, 1 would be for the decal, the other would be behind that sheet to diffuse the lighting more evenly, (the LED strips would be stuck to the back of the decal wall side), you could make it a little more complicated and try to line up strips of LED with the red lights in the backdrop but i think that may be overkill, that would make a wall mounted setup a little harder though.
