This is a great idea except for me (and for the author I suspect) I regularly come across attachment of Imgur hosted images on sites (like a post on a DIY forum but not all of them) so it wouldn't solve my issue unless I were to use your browser in the container all the time (I suspect the author also doesn't just 'surf imgur' but randomly comes across images hosted on imgur linked to from other locations).

In that case FoxyProxy's proxy by URL pattern would be what you'd want to use.