Toolman your interior looks as nice as your exterior.
I too am a big fan of rivnuts aka nutserts and have used them for many things on my van build.
I have also been using those christmas tree plastic push pins a lot.
They work really well with wood on the side and rear doors and for walls and even ceilings.
Just drill a hole and push them in. They hold great, look decent and are removable.
I made my door panels out of 1/4 plywood and used the pins to hold them on. I also covered them with carpet and I always use 3M Super 77 spray glue for all my gluing needs.