The easiest way would be to call "/opt/kde3/bin/dcop kdesktop KBackgroundIface setWallpaper <filename>". I don't know if firefox yet has a concept under which desktop it runs.
The easiest way would be to call "/opt/kde3/bin/dcop kdesktop KBackgroundIface setWallpaper <filename>". I don't know if firefox yet has a concept under which desktop it runs.