GGroundOverlay
With the GGroundOverlay you can easily insert images into the maps.
Just define imageUrl and the GLatLngBounds ...and there you have it!
Code.aspx
<cc1:GMap ID="GMap1" runat="server" />
Code.aspx.cs
GLatLng sw = new GLatLng(64,20);
GLatLng ne = new GLatLng(65,29);
GMap1.setCenter((sw / 2) + (ne / 2));
GGroundOverlay groundOverlay = new GGroundOverlay("http://googlemaps.subgurim.net/images/logo.jpg", new GLatLngBounds(sw, ne));
GMap1.addGroundOverlay(groundOverlay);