[Toni Wilen]

One sub "window" (after last image) that shows "known good" files (files that are actual text or pdf or whatever files) probably would be good enough solution?

(I missed part of original suggestion): combining image with some txt/pdf/whatever file also works. (image + "data file")

EDIT:

To keep it as simple as possible (no extra description files), what about:

"___Data_document.txt_.png" would mean if this image is clicked, "document.txt" would be opened using default program that takes .txt files. (and so on)