As far as backgrounds? The easiest and least fun is a premade background like
this. They look all right and require almost no time or effort.
You can also cover the back with
cork tiles or
coco-fiber mat. These are good for smaller lizards to climb on; in my opinion they don't look great when used alone, but can be nice as part of a more elaborate background.
If you want to invest more time and effort, you can make a more naturalistic background. Here's a how-to thread on building a 'jungle' style background:
http://www.blackjungle.com/gallery2/main.php?g2_itemId=2108. You can adapt the same techniques to match your tank inhabitants' native habitat. For example, you could make rocky ledges by attaching rough-cut blocks of styrofoam to the tank back, partially filling cracks with Great Stuff, then coating all with silicone and soil or fine sand.