User selectable option to not have images display in threads

What I'm looking for and that I think other forum owners could possibly benefit from as well, is an add-on (or perhaps it would be a template modification?) that would allow users to select an option not to have images display in threads.

This was rather handy in vBulletin for those users who are on dial-up, browsing with a mobile device, or who prefer to read content only without the 'clutter' of images. Thanks.