I've got this set up on my own site against https://www.jvt.me/img/profile.png and it's really great. No more finding that image you want to use - it's just there. It's available automagically via my Microformats2 h-card, so it can be machine discoverable, too. But I agree with Terence, it'd be awesome to have some standardised way to pull it from all my services, though.