So in the digital realm, this is easy. In the analog realm, it's simple as well—if you use a destructive process.

I'm okay with that. It's part of the presentation for me.

The question I have, though, is this: What would be the best way to handle adhering and mounting? I'm using an RC paper with a glossy surface (still want to call it F surface), and the arrangement is roughly like this:
falling_rhombus.png
I plan on cutting a custom mat for a slight edge overlap. Photo corners and wheat paste can be used on three of the four corners of the lower three photos, four on the upper one. Future endeavors may not have this flexibility, however, and the general solution must solve the problem of keeping the photos supported, decently flat, and presentable. In this case I'm concerned about the upper corners peeling away and down.

I've never attempted something like this before. The only matting I've done is in a photo class with dry mount tissue, and my Google-fu fails me on this particular project.

Thanks for any and all help!