Idea1: show the first time the npub was seen by the relay, so we users can spot new fakes 

Idea2: use one of those watermark algorithms that insert hidden fingerprints in the image, so after uploading a profile picture, even with the change of compression algorithms, the app can extract some unique identifier and compare that with the database. Clients then can check the originality of the image. It's bulletproof but can make it more challenging for impersonators