Just tossing around ideas in my head the other day on showering. Here is what I may try out in the future.
I already have a solar shower bag, have not used it yet. Just fill with water, throw it on the dash when you are driving and let the sun through the windshield warm up the water. Easy enough. This is the one that I got. Looks like this:
One idea is to rig up the back doors with a rod and shower curtain between the top of the open doors and let the water just fall to the ground. This would work when it's decent weather outdoors and not too many people around (okay, no people, haha). Will work particularly well in the summer time.
For bad weather and use indoors, my other thought would be utilizing a big cooler. I read about someone doing this yesterday and though it was a great idea. Would put where my big plastic bins are on the back passenger side area. Will store dry food inside, would also provide a good extra seating area. When needed for a shower, remove food (have them inside their own plastic bins for easy removal), hang up shower curtain, set my little folding step stool inside the cooler to sit on, and hang up the solar shower to use. Then just drain the water from the spigot out the door on the side of the van. Seems very do-able. If I wanted to get real fancy I could try to fashion a drain from the spigot out through the holes that were left from the seat removals. Just open the spigot and let the water drain under the van.
Well, those are the two options I have come up with so far. :)