Convert artwork from SVG to PNG when built

In Xubuntu Jaunty, we are converting GDM artwork from SVG to PNG buildtime. For Karmic, I would like to see wallpapers converted buildtime as well. This would for example (and especially) be a nice feature for those, whose screen resolution ratios aren't common. (The resolution ratio would be probed and a customised wallpaper built if the ratio isn't one of the common ones.)

As we are going towards SVG-only graphics (Xubuntu Jaunty actually is), this is a good way to support that process even more. Also, a normal user doesn't need the SVG files, but an artist could get them from the source package. The files would be in the repositories for the original artists to modify as well thus making it easier to push changes while working on the artwork.