Design is always better served when it comes with a side of functionality.
Website background images vary from the mundane to the vector-art overreaching to the heavy page loading. It is rare to find one that really works well. Mostly they are used for cool branding and design efforts. Sure they tell a story, but it is usually without much substanance. The recent redesign of VPS.net. afforded a look into a background image that is both a cool design and functional treatment. The global map highlights are their CDNs (content delivery networks). This PNG allows you to see the map at a better contrast:
Here is how the map is layered into the site:
Nice design. Great visual.