For flooring, we chose some really simple click-lock laminate flooring from Rona. It was reasonably inexpensive, durable, and extremely easy to install.
Our van was a Bakery delivery van in it’s previous life, so it had a 3/4″ plywood subfloor already included, however it was very… nasty. Prior to re-installing (post insulation), I pulled it out, and completely sanded it down with a low grit sandpaper to get rid of the caked on flour, the smell, and get it closer to it’s original state.
After reinstalling the subfloor, we put down a thin laminate backing, and installed the floor. We chose to completely floor the van, including the garage, and in hindsight, I am very glad we went this route.