function addIcon($iconImage,$iconShadowImage = '',$iconAnchorX = 'x',$iconAnchorY = 'x',$infoWindowAnchorX = 'x',$infoWindowAnchorY = 'x') {
    	$_iconKey = $this->getIconKey($iconImage, $iconShadowImage);
        $this->_marker_icons[$_iconKey] = $this->createMarkerIcon($iconImage,$iconShadowImage,$iconAnchorX,$iconAnchorY,$infoWindowAnchorX,$infoWindowAnchorY);
        return $_iconKey;
    }