I missed a shadow icon for use on google maps, so I created one (attached) that fits all 32x37 standard icons of this project. Below is how to use it in javascript for proper alignment:

First create 'iconshadow': iconshadow = new google.maps.MarkerImage('shadow.png', new google.maps.Size(51.0, 37.0), new google.maps.Point(0, 0), new google.maps.Point(16.0, 37.0) );

Then apply shadow to any marker: marker.setIcon('accident.png'); // any 32x37 icon marker.setShadow(iconshadow);

Excellent, I was just about to make one of these myself!