A big pool will go down or encounter copyright issues. In the end the internet is a network of physical devices on which we put stuff. If you have a couple of bucks available, you can rent a vServer and just put your stuff there and make it linkable + tagged. If a bunch of people do it, a lemmy community with a link collection could provide this. But it always needs some person to put it up, otherwise it's just back to the big corporate silos.

I'm trying to do this bit by bit by renting some machine from Hetzner, starting with a blog or sth.

Edit: Just found Pixelfed, a federated image hosting platform :D

The problem is that photos even though they look similar they are different because some people instead of saving the image they take a screenshot. I think what you say is posible but I dont know if it is worth it right now, we need to fix the bugs and then add cool features