Overlay Map Types

You can define many overlay map types this way:

var getTile = function(coord, zoom, ownerDocument) {
  var div = ownerDocument.createElement('div');
  div.innerHTML = coord;
  div.style.width = this.tileSize.width + 'px';
  div.style.height = this.tileSize.height + 'px';
  div.style.fontSize = '10';
  div.style.fontWeight = 'bolder';
  div.style.border = 'dotted 1px #aaa';
  div.style.textAlign = 'center';
  div.style.lineHeight = this.tileSize.height + 'px';
  return div;

  index: 0,
  tileSize: new google.maps.Size(256, 256),
  getTile: getTile

You must define a function called getTile, which returns a HTML element used to fill the map overlay. Also, you have to set an overlay index, which place the overlay on top of the base map, according this index.

NOTE: You can remove an overlay map type using removeOverlayMapType(overlay_index).