for (var i = 0; i < activityIds.length; ++i) {
  var desktop = activityById(activityIds[i]);
  desktop.wallpaperPlugin = "image";
  desktop.wallpaperMode = "SingleImage";
  desktop.currentConfigGroup = new Array("Wallpaper", "image");
  desktop.writeConfig("wallpaper", "/usr/local/kde4/share/wallpapers/stripes-freebsd-blue/");
}
