Not very good pictures but here is mine.
Made the trailer itself about 12 years ago and made the enclosure 3 years ago.
Used 3/4 square tubing for the frame work and covered it with aluminum. Than insulated it with 3/4 polystyrene.
Made the back out of some Naugahyde material. Roll it down and have velcro on the side of the trailer to hold it in place with some hold down straps. It's worked fine for me.
Wallygator just finished up his enclosed trailer if he will ever take some pictures and post them out. Looks a lot better than mine.