Do you want to know how the CSS WG works? Fantasai has written about:csswg, An Inside View of the CSS Working Group at W3C.
The CSS Image Values and Replaced Content Module Level 3 specification has been published as a W3C Candidate Recommendation. This module includes syntax for CSS gradients, image slices, and fallbacks; as well as several properties to control replaced element sizing and rendering.
W3C encourages everybody to implement this specification and return comments to the (archived) public mailing list firstname.lastname@example.org (see instructions). When sending e-mail, please put the text
[css3-images] in the subject (alternatively you can email one of the editors and ask them to forward your comment).