I did not want to be worried about my pictures falling and did not want to be taking them down while in transit so on my previous trailer I attached my large pictures to the wall by a single screw and applied a bead of silicone around under the edge. Pictures stayed put. When removing the pictures to sell the trailer I used the flat blade of an exacto knife to carefully separate the picture from the wall. I than rubbed the remaining silicone off of the wall and used a bit of white Dap caulking to fill the screw hole. You could not tell that I had hung a picture on the wall when I was selling the trailer.
One bit of caution
. I accidentally used liquid nails caulking on one of the pictures instead of silicone caulking. After many hours I did manage to get the picture removed and the remaining liquid nails off the wall without any damage. It was a horrible ordeal.
I am going to soon hang pictures in my new trailer using a single screw and small bead of clear 100% silicone just under the picture frame edge but inside enough so that it does not squeeze out when the picture is pressed against the wall.
Good luck with whatever you decide to use