When I first started trying to create a website, sometime ago, I just knew the theme had to be one of light within the darkness. Because, let's face it, the world is a very dark and chaotic place to live in (once you become self-aware, at least).
So these are the 2 photos I first used, as background wallpaper, when creating the website as an expression of the perceived self vs. the perceived world.
This was used also because of Plato's allegory about "The Cave" and how most people would rather stay inside the cave rather than wander outside into the painful light. Just google it and you'll know what I'm talking about -- but I'd rather you read the original works and REALLY understand where I am coming from...