var clusterStyles = [ { textColor: 'white', url: 'path/to/smallclusterimage.png', height: 50, width: 50 }, { textColor: 'white', url: 'path/to/mediumclusterimage.png', height: 50, width: 50 }, { textColor: 'white', url: 'path/to/largeclusterimage.png', height: 50, width: 50 } ];