All the truck and camper mechanical stuff is my department. I told my wife - an ex pro painter - she could do whatever with the interior she wanted.
First thing she wanted to do was paint the whole thing. I was very skeptical but hey it's just an old camper. It was very labor intensive because a truck camper is pretty much all corners and edges inside.
It looks eleventy zillion times better! It was all typical old camper brown wood, now it's aqua colors, a lighter base with a slightly metallic darker trim, looks great and feels "bigger".
It's been done a few years now and has held up great. Plus it's easy to fix if you do damage the surface.
She just thoroughly cleaned it then primed & painted, didn't sand.
The whole inside is "glamper"-ed out, no one expects it to be so nice inside when it's just an average old camper outside. And I only paid $1500 for it, about 7 years ago!
It's amazing what well-done paint and fabric and contact paper can do for a cheap old rig.