More complex icons will want to specify complex shapes (which indicate regions that are clickable), add shadow images, and specify the "stack order" of how they should display relative to other overlays. Icons specifed in this manner should set their icon and shadow properties to an object of type MarkerImage.
Shadow images should generally be created at a 45 degree angle (upward and to the right) from the main image, and the bottom left corner of the shadow image should align with the bottom-left corner of the icon image. Shadow images should be 24-bit PNG images with alpha transparency so that image boundaries appear correctly on the map.
MarkerImage objects not only define an image, but also define the size of the icon, the origin of the icon (if the image you want is part of a larger image in a sprite, for example), and the anchor where the icon's hotspot should be located (which is based on the origin).