Okay, so the folks from Westfalia were pretty clever in their use of space in the Vanagon chassis. But just were is there to store the stuff you need to take with you.
This is a listing of the storage spaces and other places in the Westy. It's absolute trivia unless you're trying to figure out how to pack everything into just the right space.
Cabinets under sink
Cabinets between closet and fridge
The mirror in the closet door of our van (don't know if it's standard) is 4 5/8 x 21 3/4
Under the Back seat
Space behind the backseat, don't forget to plan room for the closet door to swing
Rear closet (behind back seat)
Free space in light valence (lightweight, no metalic stuff only)
There is also a small compartment accessible only form the rear hatch which I haven't measured yet.
Other potential spaces which I haven't investigated