Here's a few photos of my setup. Oru Designs Bruin camper on a 2006 Nissan Frontier 6spd. I’ve had the setup for a little over a year and 35,000+ miles. I’ve taken it to both coasts, up to Canada, down to the southern border, and all over the Rockies. Usually skiing Loveland or A-basin, with trips to Wyoming, MT, and New Mexico every Winter. Many nights below 0ºF, and the coldest we've seen so far is -35º.
I’ve been slowly building out a DIY interior with an insulated floor plate, kitchenette, and ski cubby bench. I’ve got a 100ah LifeP04 battery setup that charges off the alternator with a fuse box that runs an Iceco GO20 fridge and a power panel above the table. A small sink with a 12v pump on a switch, some cheap plastic drawers, and usually a diesel heater complete my relatively simple setup. I then use a 4" tri-fold queen mattress that stays up top when the camper is closed.
The floor is a 1" pink foam + wood sheet construction (1/8" base & 1/2" top) with vinyl surface and wrapped in silicone tape with a seal on the front edge that seals to the tailgate. Then a bedrug on top in the Winter to mitigate water. The kitchenette and cubbies then bolt to the wood floor with threaded inserts so they’re quick and easy to remove. The floor comes out in two pieces so it can come out with the camper top still on. It takes about 15 minutes to remove the entire interior and can be done by one person.