There are instant film backs for the medium format and the large format cameras. These are used as they were originally intended with out of date Polaroid and new Fuji instant film in Polaroid or Fuji instant film backs. These are great already finished photos and have a wealth of information before using real film in the cameras. They are great objects on their own. Many outdated 4x5 Polaroid film packs from a friend will be shot to be sewn into a large piece. The first pack was tried, a little blue and long exposures, but it has possibilities.
Nerd Alert - The photos shown have chamfers that are the telltale of the total opening of the Mamiya RZ67. For film there would be masks in the film backs that would limit the image to 6 x 7 cm. The instant film backs don't rotate for landscape or portrait like the film backs. The instant film backs, unless they have horizontal or vertical mask inserts will show a 7 x 7 cm image with 5mm chamfers.
For more information about instant film, see Blog entries for the Double Exposure Project.