There is a separate background associated with each blog post (although at the moment many still have the default). This is done by putting the url for the background in a custom field in the post. The post template has a bit of CSS at the top of the page which adds this background as well as custom colors associated with it.

On the home page the background is pulled from a random piece in my portfolio, which is also featured at the top right of the page. I use a custom query for this with showposts set to 1 and offset set to a random integer.

While reading the post, I saw that you have a custom background.
Is it random, or do you define witch image goes for each page/post?
How did you do this?

Thanks, and great job with the layout!