I have a background. I have "heard" that it helps the geckos out a bit seeing as how they don't like to be in wide open areas and it lets them feel more enclosed. Of course, it's all speculation and background is fairly cheap so I bought some.
When I got my first leos I wanted everyone to have a nice looking background and I spent a bunch of time on it. Now, with 16-18 cages and a 32-tub rack, all of which were full at the height of baby season, I don't have the time. Everyone is just fine without them. A few years ago I decided I should tape some colored paper over my plexiglass dividers so the hatchlings in the different sections couldn't see each other. One day I came in to find one of the hatchlings had somehow managed to scale the divider and gotten caught in a loose piece of tape so she was actually taped to the divider. Now the dividers are clear and they cope just fine.
I don't have any backgrounds. Just the tank, the substrate, bunch of hides, food bowls, and calcium dish. I guess I'm a little boring. But they hide all day and are color-blind, so what do they care? And I'm mostly apathetic to decor.
Well I have 5 tanks now and they each have backgrounds. Four have the standard desert background but with my last tank, they were out so my son talked me into a dinosaur land background! Pretty cute really and Sophia does stare up at it. Wonder if she thinks the Brachiosaurus is a giant gecko or some other scary creature. haahaa LOL!
Two of my tanks have paper taped to the back, and the other two have spraypainted backgrounds. It does help the animals feel more secure, and It looks better, to boot! (Hides those pesky wires and such.)