I work a lot of puzzles and use a product called hod podge to bind them together, I would think you could use it as an adhesive to bind to the wall, but what to cover it with, I don't have a clue. I would assume sometype of sealent. I also refinish furniture and sometimes add pictures of flowers or animals then seal with furniture varnish, I don't know if it would work on a wall, but maybe you could try on a small spot and see how it goes. Just a thought but maybe you could go to a craft store like Micheals and ask someone they might know.