Were you upset when Firefox changed the way it started to show regular images in the browser? I don’t mean on a webpage, but when you look at a single image after typing it’s location into the address bar. Bug 376997 added a stylesheet to top-level images that forces the background to black and centers the image. This extension removes the stylesheet, returning the background to your configured default and removing the centering.
This is a fairly simple extension for Firefox that gives you a few more options (other than fixing the issues mentioned above). There are also options for setting a custom background color or a checkerboard background, and for re-centering the image and removing the margin, so if you prefer some different combination of styles you can set that too.
Want to restore the default image style used for top-level images to how it looked in previous versions of Firefox? Download Old Default Image Style from the Firefox Add-ons website.