There are a few good threads on this topic that I've been reading on the Popup Portal Forums.
Some guys are using the Automotive LED strips that are one continuous strip and mounting it to the rear bumper. Doesn't protrude more than about 1/4" from the surface, and provides a uniform backup light.
Others are using little 4" 18W or 27W LED flood lights that are mounted slightly inboard of the bumper end, and angled in such a way to provide light behind and off to the side a little. This is what I'm going to do shortly. I found some nice ones on Ebay from this guy -- Powerbulbs
What I'm going to do is place them on my back bumper rail, tucked in near my spare tire mount, angled 30* off to the side or so. I'll play with the light position so the edges of the beams meet behind the camper and give me a decent flood.
Most recommend just wiring a fused line to a waterproof toggle switch and the battery. This way, when you get to a site you scope it out anyway by walking behind the camper first, just throw the toggle and you are good to go.
If you are an in-depth electrical guy, there are also discussions on relays and wiring to your TV.