Wikimedia Commons, the English Wikipedia, and hundreds of other sites have added this to their [[MediaWiki:Common.css]]:
/* Put a checker background at the image description page only visible if the image has transparent background */
/* You may want to clear the gallery background for the main namespace on other projects as galleries are used in articles */
#file img,
.filehistory a img,
.gallerybox .thumb img { background: url("http://upload.wikimedia.org/wikipedia/commons/5/5d/Checker-16x16.png") repeat; }
It should be in core.
Version: unspecified
Severity: minor