I think this is the simplest way to implement a favicon:

• Turn the site's favicon.ico into a png and put it in db/site.
• Implement a clause in controller.xql that intercepts requests for it from any folder or subfolder and serves it appropriately.
• Add this to the header include:

  <link rel="icon" href="favicon.png"/>
  

Not quite sure how we serve out the image file yet -- it may require an XQuery with binary-doc().