Web Page Backgrounds Are Supposed To Be Ugly
Ok, maybe not. Before reading this, note that I'm really not a designer. This is just a post about a book I read, and a thing I learned. And it's probably wrong. All of it is probably wrong.
After reading "Fresher Styles for Web Designers: More Eye Candy from the Underground" by Curt Cloninger, I learned that web page backgrounds are, most of the time, supposed to draw attention away from themselves, and into the content. Cloninger actually refers to background styles as "background killers", because the goal is literally to take void space, and remove it from the site, draw attention away from it, pretend it isn't there, and/or put it in a special dimension where users won't even know it exists.
At this point you may be thinking that I'm just stating the obvious, so hopefully you and I can share a moment here:
Do you ever recall designing a web page with a minimal amount of content and a plain color background, looking at your work and thinking about how horrible it looked? I certainly can, and it's because I didn't realize that to make a nicely laid out page, you often need two dynamic backgrounds styles, not one flat one.
Having two backgrounds is a subtle thing, but I promise you that many of the sites you look at will use two background styles. One background for the actual browser viewport itself, and one background style for the content. With the exception of the sites that are chock-full of content, designs will often employ two backgrounds to drive the valuable information to the eye of the user.
This makes sense because you usually don't want your body copy/content to sit directly on top of the browser viewport background, especially if you have a gradient background, a heavy pattern, or an image. Using two background styles in this way directs your users' eye to the content of the page, not the empty space around it. It then becomes incredibly easy to determine what part of the page is valuable and what part of the page is empty.