Image Hosting - Different Domain, Subdomain, Beneficial?

[PROFRBcom]

Was running some speed tests at tools.pingdom.com on this page and it returned these optimization results. Overall the page scored pretty well but one particular suggestion to optimize the page caught my attention:





I take this to mean that it is recommending that we host images on say, images.website.extension rather than website.extension and that by doing this, it would reduce network traffic and in theory, increase loading speeds.

I have seen a website before, I believe it was PokerNews actually, use some different domain for hosting their images. Perhaps it was pnimages.extension or something to that effect.

Has anyone tried using a subdomain or an entirely different domain to host pictures in order to speed up their site performance? If so, I would love to hear results!