I bought this trailer for $75 off of Facebook Marketplace and spent a couple of weeks freshening it up. I wire-wheeled all the old paint and rust (and moss) off, and then repainted the frame and expanded steel floor. Then I made a new tailgate out of some square tube from the dump and new fenders out of a 55gal drum also from the dump. Next, I swapped out the crusty wheels and tires and replaced the taillights and wiring. I also added some 1x6s around the sides and front to create a bit more of a wall, and just make the trailer look a bit nicer.
After struggling to fit 4x8 sheets of plywood or steel inside the trailer (it being exactly the same size, meaning that you couldn't get your finger under whatever was in the trailer), I made a set of "roof racks" to use to firmly strap stuff slightly above the deck of the trailer. Saving best for last, my favorite part of the trailer is the little support leg, with a foot-shaped foot I made.
I use my trailer pretty much weekly to tote all kinds of things around, from small farm equipment to materials for projects.