Here's a really clever idea from site-specific game creators Invisible Playground. Their website uses Google Maps satellite view as a background image. The background isn't a static image but is a fully interactive map centred on Berlin.
But that isn't the clever bit! When you drag the map around the map also moves for everyone else viewing the webpage. What's more every move of the map is recorded and Invisible Playground plan to post a map soon tracking where user's have dragged the map.
- Set Google Maps as Your Page Background - A short tutorial on how to set Google Maps as the background to a website using z-index
- Google Maps Road Trip - Google Maps Road Trip use a static image from Google Maps as a page background
- EarthWallPapers.net- Looking for a new desktop background then choose one of these cool Google Maps wallpaper backgrounds