User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:15.0) Gecko/20100101 Firefox/15.0.1 Build ID: 20120905151427 Steps to reproduce: Open an image-only URL (e.g. https://bugzilla.mozilla.org/extensions/GuidedBugEntry/web/images/products/firefox.png). Look closely at the gray background (you can take a screenshot and zoom it to improve visibility). Actual results: Instead of a monochrome and homogeneous colour, the background looks noisy, consisting of (in my case) four different shades of gray. See attachments for an example. Expected results: The image background should exhibit a homogeneous look, consisting only of a single colour.

I added a new screenshot that shows maybe better what the problem is. The screenshot shows http://www.mozilla.org/img/covehead/template/title.png. I edited in an area of clean gray with the mean color value of the site background to show the difference between a monochromatic are and the noisy background. Additionally I edited in a clean white area that shows that now also the background of transparent images is noisy (which is bug 848018)

The texture on the grey background is intended and there aren't any plans to change it going forward. You can install the https://addons.mozilla.org/en-us/firefox/addon/custom-image-backgrounds/ add-on to change the color of the background if you would like.