Curiously I recently ran a page speed test of index page at http://www.background-checks-systems.com and noticed it responded with 34 http requests due to plenty of image lookups that were not in that page, but rather in other pages of site. A bit perplexed, I further researched as to see why.
It appears that when I merged all css files into one global file, many divisions contained background css images although not rendered by index page, but listed from other pages in the site – it still created unnecessary http requests when robot crawled css file link.
I ran additional test by placing css directly into main page using after getting rid of all unused styles from global css file and amazingly my first view http request went down to 14 from 34, file size decreased by more than half and load time down to 1.061s from 4.32s
Perhaps this method may work for your high-traffic pages (if not, at least your index page) whereby you can still call your css link for formatting while creating in-page head css file for background images.
Logistically it may seem like a bit of work, but keep in mind that is only for pages that contain different image backgrounds. If the same background is used more commonly throughout the site, by all means leave it in your main css file.
Anyone else experience this? or maybe I was just ignorant to this?