Doug,
I painted the floor when I first got the trailer, before it had anything loaded in it.
I used an
oil based floor and deck enamel, in a medium grey gloss. Thin the first coat and use it as a sealer, then brush the second coat on and let it dry for about two weeks. It has held up great.
If you want a non-skid surface, they make a sandy additive to mix in the paint, or the truck bedliner would work also.
Mine has the luan paneling on the walls, with a white vinyl ceiling. I finally got around to painting the walls with white exterior gloss latex. It really brightned up the interior, but I still got some bleed-through even after two coats. (Heck, it ain't the living room.)
Jeez, even our trailers are projects.
Later,