I admin a small instance as well and I have only blocked lemmynsfw.com at this point. I like to keep the server open to all unless a rule is broken on my server. This means even if I don’t agree with what is be said, again, as long as it is within the rules of the site.
It baffles me as to why you would go through the trouble of creating an instance and just leave it to rot with no oversight.
Don't want to deal with possible issues related to the cached images being stored on the server.