Scratches on iPad back, any other ways to prevent it from happening instead of buying on huge iPad cover?

I don't think there's an easy way to repair. You don't want to take any sort of machine or polisher to the back of th e iPad.

About the only thing I can think of that meets your criteria is a snap on or silicone case for the back, or perhaps a Zagg full body cover....which is like a screen protector that goes on the back.

YOu want to protect it you're going to have to accept some addition of bulk because the only way to protect it is to cover it.

You could look at a skin, such as those sold by Stickerboy.net:

http://www.stickerboy.net/pages/tablets

I've purchased several skins from this site for my iPhone and MacBook Air. I'm impressed with the quality and selection. The skins are basically industrial-quality films with adhesive on the back (made by 3M I believe). They've applied the adhesive in a way that leaves no bubbles when the skin is in place. It's really amazing. They come in many styles and colors, including wood-tones, carbon fiber, leather-look, etc. I think they may have a clear skin too. If you want to protect the back of your iPad without resorting to a case or sleeve, this might be your ticket.

I purchased my iPad 2 last July. I only use a black leather Smart Cover on the front, nothing covers the back. When traveling I carry my iPad in a home made cloth case. When using my iPad I always have it on my lap or a placemat at a table or desk. I keep it on a cloth napkin when it is resting or charging on my counter.

So far there is not one scratch on the back of my iPad. The best way to keep scratches from forming on your iPad is to take good care of it.

I'm just as careful with mine save the napkin. The only scratches, ironically, are from the smart cover where it magnetically clips. I got a rather large one on my iPad 2 near the bottom and just discovered 4 small ones in about a perfect square of space. Basically, just be careful and set it down on soft surfaces. Wood isn't too bad, but I generally like to set it on a tablecloth or face down on the smart cover if need be.

You might try a skin such as those by Decal Girl. They come in a great variety of styles and add no thickness to the device.