Be careful trying to mount shelves to the walls. Not very thick, and make sure you know what is behind there. Had one customer attempt this on a Shasta, and shorted his cable TV wire, to a 110 Volt AC wire. Was a mess to fix, and not under warranty because he caused the damage. If I put shelves in, I would put them on legs, inside the cabinet.
Now with that said, remember, anything sitting on shelf, while traveling, will probably be on the floor when you arrive at your destination. Maybe in one piece, maybe in several.
Not trying to say don't do it, it's your camper, do as you please. Just think it through.
2012 Ford F250 ext. Cab 4x4
2002 Jeep Wrangler Sahara
2008 Yamaha V-Star 650 Classic
2008 Work and Play 18LT