I've always liked them best with discrete archway, headlining, some ply on the floor and some durable carpet on the floor and on the sides up to the ute top that neatly covers the wheel arches. I have seen some sort of felt like material used on the van sides up to the jeadlining that looks neat too. Means you can still use it for carrying stuff, or you can throw a matress in if you like. Thee is plenty of room on the back of the removable side panels for speakers or 12V sockets, or even to recess and hide an inverter. If you are running lots of 12V stuff it doesn't hurt to hide a sealed 12V battery up under the floor with a diode protected feed from the alternator so you don't flatten the car's battery.