You could also just steganographically encode it. You have the entire URL after the domain name to encode leaked data into. LLMs can do things like base-64 encoding no sweat. Encode some into the 'ID' in the path, some into the capitalization, some into the 'filename', some into the directories, some into the 'arguments', and a perfectly innocuous-looking functional URL now leaks hundreds of bytes of PII per request.

I'm not sure I'd allow all those random base64 encoded bytes for a simple image url.

That's not a solution. You have to guard against all image URLs, because every domain and path can steganographically encode bits of information. 'foo.com/image/1.jpg' vs 'fo.com/img/2.jpg' just leaked several bytes of information while each URL looks completely harmless in isolation. A byte here and a byte there, and pretty soon you have their name or CC or address or tokens or...

Maybe you didn't read the last part of my suggestion:

> showing the call details.

If you really want to render an image, a huge base64 blob would be a bit suspisouse for a url that should simply point to a png or similar.