jQuery Fullsize Plug-in
Even though Fullsize is not currently in the next HTML spec, you can still get Fullsize for FREE! they created a jQuery Plug-In that does just what is described above and what you see in the video below. Since there is no fullsize attribute for the <IMG> tag yet, They using the longdesc attribute instead. longdesc is a completely valid image attribute and is meant to contain a URL to a description of the image. The Fullsize jQuery plug-in is super easy to use, and provides a kick start to standardizing the way image pop-ups look and work.