I will assume that
a) you don't have picture rails,
b) the precious walls are papered or beautifully painted,
c) you want to hang pictures rather than posters or prints.

My only suggestion is to drill holes in the ceiling close to the wall to put in plugs with screw eyes, then use strong brass wire or nylon fishing line to hang the picures. You will need to be extremely careful that you dont make a mess of the ceiling, especially if there is an elaborate plaster cornice, so think about the eventual reclaim of your deposit.
Posters or prints can be fixed with blu-tak and similar sticky fixers, but they often leave a stain; another method is using pins, which leave very small holes.