Whatever the theme, magnet posters (magnetic-metallic) for fridges, but also for your walls.
Save the cost of a frame, avoid drilling holes in your walls with 3M adhesive tabs : they attach without damaging the walls, and they can be removed cleanly without leaving any residue, and it will only take you 30 seconds. So change your posters as often as you like... start collecting them, repositioning them, changing them...
