What we did:
Our latest build is this 170” WB 4×4 sprinter with Aluminess bumpers and nerf bars and a really cool black interior. After insulating with Thinsulate we paneled it with black aluminum paneling and with all of the windows, the van has a really nice light inside. Taking a page from my and the owners background (he is a world renowned custom boat builder) we installed a pipe bunk for sleeping, but we added a twist by putting it on sail tracks so it can be moved up and used as a storage shelf, lowered down to sleep on, or put all the way to the ceiling so it is out of the way when not needed.
A Ruhne Racing house battery system powered the Fantastic Fan, LED interior lighting, and outlets for an ARB fridge. Full runs of L Trac down each side allow for interior components to easily be anchored in or to strap down cargo. Seat swivels round out the interior.