Here's a few on the list:
Get a bin attached to the back. I'll look into welding on some reinforcement so I can put a hitch receiver back there. I need a place to put the folding chairs and other camp site stuff. Mainly light-weight items. Heavier stuff can go in the back of the truck (it has a cap).
Cindi has some ideas for adding extra shelves in a couple of the cabinets.
Add a marine battery switch to isolate the battery when it's not being used.
Vent covers for the roof vents.
Larger table to hang on the grill rack on the outside. I don't plan on using the RQV grill, so I can take advantage by having a little more "counter space" outside.
Add a 6" PVC pipe underneath for storing indoor/outdoor carpet.
LED light bulbs for interior light fixtures.
That should keep me busy for a while...