With PNGs people need to start hashing the decompressed RGBA pixels, instead of the raw bitstream.
For PNGs at least, that would solve this forever. Same pixels = same pixel hash - even if cloudflare compressing their PNGs better or file metadata or whatever fucks up the file hash.
Should work with GIF and *maybe* jpeg too.
Problem is, you'd need to build-up a database of file->pixel hashes (for an existing archive, that'll take awhile), and add a thing in the frontend UI to make searching them easier.
Will anybody do this? Nope, because I don't have the skills, and nobody who does will read this.
Also I'm not sure if this frontend/archiver software is even still in development.