I've meant to add this for a while but keep forgetting. I'll try to get some better photos too.
A while back I built a platform for the rear seat area. For longer trips when I don't need the rear seat, I pull the seat and the platform installs using factory holes. There are several different tie downs on the passenger side. I usually just have lightweight items or snacks, or camera gear that I don't want in the bed. Also allow some storage underneath the platform for some recovery gear and tools.
Kinda hard to see in this photo but the driver side is my ARB fridge that is mounted on a FrontRunner slide. The hinge for the fridge lid is toward the door so that the fridge is easily accessible inside the truck without having to slide it out. But can be accessed from the outside by opening the driverside rear door and pulling out the slide. Gotta say it's easy to get spoiled on longer trips when you have a fridge. No more dripping wet items inside a cooler of ice.