Thanks all for the information! As it turned out, I happened upon 3M Photo Mount, a single-surface aerosol contact adhesive. Though I admit it wasn't the solution I truly desired, I got the collage put together the way I wanted. 'Sides, the subject is really pleased with the result as he assures me his wife will be.

Disclosure: The photo of this mounting was from a digital camera, and some manipulation has been done to the digital image to remove identifying brandmarks.

mounted.jpg

The total mounting size is 16"x20".