I would like to be able to set the horizontal and vertical components of the background-position and -size independently. Currently this is not possible. [css3-background] is at candidate recomendation, and [css4-background] (http://dev.w3.org/csswg/css4-background/) doesn't mention either property.
T'would seem someone had this idea before me, as WebKit already splits background-position. Altered title accordingly.