I think we should be able to have the option to store images locally. Say for instance someone tries to backlink a picture in their signature or post by storing it on their server and then posting it to your website (basically what I'm doing right now, for example; right-click my signature and open it in another tab). You should have the option to take the remote URLs/data and store it on your website's local server, cutting out unwanted backlinking and whatnot; that way links and content would show as if they're coming from your website, not from an external source. I think a lot of forum owners would find this option very useful.
I love this idea as it could also help save old threads from displaying broken images which over time can ruin a thread, The only problem I can see is such a feature may be looked at as a type of scraper and allow copyright infringements.
It has my support, though it might be a good idea to propose this as an unofficial add on.
I thought all links posted by anyone that's not a moderator or admin were Nofollow attributed... which makes me think that backlinks should not be an issue as it won't help them spam their way to success.