I just thought i'd raise why this is still a very valid and important feature request.
The problem here arises because for organisational purposes on large or multi-part sites such as ours, we have separated files for different application components... such as our movie news and our tv guides sections of the site.
These are kept in separate files for easy compartmental workflow of the team as well as reducing file size of all css when minified on the fly by the server. If image references are shared between css files (h3 or h4 decorations, gradients, etc) because of common styling, then the above way of writing code isn't applicable, because of the split files.
eg:
Movies css:
.movies-header { background-image: url("../img/deco.png"); /** sprite-ref: sprite */ }
TV css:
.tv-header { background-image: url("../img/deco.png"); /** sprite-ref: sprite */ }
An inconvenient work around could be forced with an additional css file which overrides selectors with the applicable background image of all the separate css files and defines all the backgrounds there. Like "backgrounds-all-over-the-site.css". This is however, highly impractical and a nightmare to manage! 
I just thought i'd raise why this is still a very valid and important feature request.
The problem here arises because for organisational purposes on large or multi-part sites such as ours, we have separated files for different application components... such as our movie news and our tv guides sections of the site.
These are kept in separate files for easy compartmental workflow of the team as well as reducing file size of all css when minified on the fly by the server. If image references are shared between css files (h3 or h4 decorations, gradients, etc) because of common styling, then the above way of writing code isn't applicable, because of the split files.
eg:
Movies css:
.movies-header { background-image: url("../img/deco.png"); /** sprite-ref: sprite */ }
TV css:
.tv-header { background-image: url("../img/deco.png"); /** sprite-ref: sprite */ }
An inconvenient work around could be forced with an additional css file which overrides selectors with the applicable background image of all the separate css files and defines all the backgrounds there. Like "backgrounds-all-over-the-site.css". This is however, highly impractical and a nightmare to manage!