menu_FileQuitItem {
  list-style-image: url("moz-icon://stock/gtk-go-back?size=menu") !important;
  -moz-image-region: rect(0px 16px 16px 0px) !important;
}

menuitem[command="cmd_delete"] {
  list-style-image: url("moz-icon://stock/gtk-go-back?size=menu") !important;
  -moz-image-region: rect(0px 16px 16px 0px) !important;
}
menuitem[command="cmd_delete"][disabled="true"] {
  list-style-image: url("moz-icon://stock/gtk-go-back?size=menu&state=disabled") !important;
  -moz-image-region: rect(0px 16px 16px 0px) !important;
}