Depending on the chemistry of the image production, it may not need air inside, and could work similarly if it was a solid block of glass, so maybe that would b

Depending on the chemistry of the image production, it may not need air inside, and could work similarly if it was a solid block of glass, so maybe that would be an option. Attaching the "film" securely in a removable way might be tricky, so maybe you don't remove it, just look at or scan the image through the glass.