Overview
This is a basic appengine-based app to handle server-side map tile overlay as a custom map source.
It is currently deployed under "http://tilesource-153122.appspot.com/composite/{z}/{x}/{y}.png".
For example: "http://tilesource-153122.appspot.com/composite/15/5335/11574.png"
Max zoom levels of 7-17 appear to work...