Command Hooks, been using them for years and years now. Current camper has one hanging on the door handle. I put it there to hold the outside thermometer wireless sensor. That Command Hook has been there over 4 years now, in all kinds of weather and has not come off.
We have several inside the camper we use for different purposes. Put one on each side of the bed to hold a night robe for easy access. They've been holding those robes for 4 years now, even bumping down the road.
Command Hooks are probably your best. If hanging picture frames, use the hook, then add a bit of double sided tape to the back corners of the frame and attach to the wall. This will keep them from flinging off when in transit.