The software I am using (FOSS) provides functionality that allows the user to link to their uploads in a multitude of formats. In the backend, it stores all images as QOI format for efficiency reasons. Upon request at a generated URL, whatever format they request is generated and cached for a time period.
This is a minor thing. Other image hosts resize images for smaller screens to save bandwidth. Data usage is already a top complaint I hear from fellow nostriches, so I think these things should be considered inv your planning. Images are heavy, and we should eventually be able to optimize for that.
Again, I love the idea of tamper evidence, but wondering how this can work. Is there a way to use perceptual hashing?