I'm curious of the 2021 measure of total disk space that Discord consumes. Servers that I'm in share images every few minutes, which must add up pretty quick.
I'd imagine a hash like SHA256 would be tricky because if that image was compressed an additional time at all throughout it's internet journey, then we'd get a different resulting hash, but maybe there is an effective way to fingerprint images. I have a utility on my machine (czkawka maybe?) that does really good image de-duplication with what seemed like a common algorithm (based on a quick look at the source).
No idea though, just spit balling.