If you look closely at the header here, you'll see that it's actually using a repeating image to give it texture. This makes for something a little more interesting than a blank background.

You can use images in other ways as well: the image element will let you pull in images of your choice. For Example:
    

Note that when you hover over the first image, you get a description: This is from the title attribute. The second text has a broken link, but because of the alt attribute, text shows instead.

Images can also be links: check out these arrows.