built a leveling platform out of 1/2" wood using (3) cut down 2x4's for legs. It's bolted down in (4) locations to the vehicle where the original D-rings are and has a slide out table that I use all the time. I also removed the 60% back seat and built a platform this time using some metal legs I welded together that bolt to the original (4) seat mounting points.
I covered the entire thing in some indoor/outdoor fabric I found at Home Depot that basically matches the interior so the entire thing looks surprisingly OEM. When I camp in there I like having the carpet, it's more cozy, although less resilient to water/dirt so something to consider.
After that I use my sleeping pads, but recently upgraded to the
Extra Large KLYMALOFT Sleeping Pad. Sorry no pics of everything all together. Just imagine two full size pillows and some blankets all in there :P
If you're interested in any details let me know, I made some videos or can provide more pictures/information.
I also made reflective window shades for all my windows out of a roll of Reflectix I bought from Home Depot. I punched holes in it along the top so I can keep the windows cracked with my rain deflector thingies and have some air flow. In the summer I have a fan I use.