Well, it's interesting. My main concern with capturing the entire tab as image is that the site being captured maybe one of those infinitely scrollable pages (i.e. same as the history.html page) in which case, depending on implementation, the tab may be very very long (tens of thousands of pixels in height) and 99% blank (if employing an infinite scroll mechanism that puts only the currently viewed items in the DOM)

Edit: so capturing on each scroll step (over say 3 seconds) > $('body').height()/3 and grouping the multiple screenshots under the given item is one possible way. Thanks for your thought.