Well I don’t think all images would have to be authenticated, just photos you take on social media and dating apps also seem like a good potential use case, if you want to prove authenticity.

You could of course fake green checkmark but this is already an issue with faking browser UI elements, including address bar–it’s a known problem.

One way to solve this is having a browser picker, that is a button you click in trusted area of browser UI that lets you inspect any image on the page. Similar thing is possible with smartphone UI, you go to app overview/carousel and long press on an image in app this launches photo inspection portal.