title: Custom Map Tile Overlay Issues
body: <p>I have a need to display a couple hundred to perhaps one thousand high resolution aerial photographs over the standard satellite imagery provided by Google maps.  The images are geographically dispersed, so I decided to implement a tile server as a generic asp.net handler (*.ashx file).  I will be basing my issue descriptions on the map shown on Google's developer site at the following URL:</p>
  
  <p><a href="https://developers.google.com/maps/documentation/javascript/examples/maptype-overlay" rel="nofollow">https://developers.google.com/maps/documentation/javascript/examples/maptype-overlay</a></p>
  
  <p>Everything is more-or-less working, but I am having the following two issues:</p>
  
  <p>1) After selecting the "Satellite" map type, hovering over that button produces a dropdown with a checkbox called "Labels".  How can I add another checkbox to that dropdown titled "Aerial Photographs" that will toggle my overlay on/off?  Will I have to hard-code JQuery hacks that utilize Google Maps implementation details, or can I accomplish this through the API?</p>
  
  <p>2) My *.ashx handler returns either the image, or a status 204 (no content) if the specified tile does not exist.  The issue is that the 204 results are not cached, so every time I zoom out and back in to the same location, my server gets re-hit for all the tiles that the client should already know don't exist.  I failed to see it documented what a tile server should return for such an "empty" tile, so the client can cache the result.  What should I return if there is no map tile for a specific location?</p>
  
  <p>Thanks.</p>