I wouldn't put bedliner on it, but I'd put either steel, aluminum, or Stainless. If you don't want to go that route, I'd look into rubber runners, Formica, a stall mat, or even Masonite. Something that can be easily swapped out or tossed when it gets real bad looking. You could even go to a recycling place and ask if you could cut the side(s) out of a refrigerator.