If you had put in the terms of your OpenSource Image Hosting platform that users couldn't use the software to host violent or simulated violent content, that restriction is removed by CC 4.0.
Conversely you can now require that anyone who uses your Image Hosting Platform gives you the rights to any data about users of that platform. This will probably only hold in Europe since in the US data is pretty hard to copyright.
It also now allows that if you are a Model in an image that is shared as Creative commons that if someone wants to make modification to that image to make it look like you are being Raped, or raping someone else that is permissible, and you can only say all derivative works are allowed, or none are allowed.
This is a major step backwards.