There’s also the case where the link just turns bad and is out of your control. E.g. when using link shortener and they recycle the urls.

Now, your image may point to completely different picture (or 404).

If there’s no image hashing/UUID signed by the author this does not sound very solid solution.

What would it look like to have ephemeral asset URLs?

Can the links be assigned and maintained dynamically / periodically enabling moving assets from one domain host to another.