It appears that you are using the Website Wizard. To change the background properly you should either have access to your web page's
tag or the body style definition, in the CSS file. But the Wizard doesn't give you access to either one of them. However, it is possible to change the background.
I don't necessarily recommend a picture for a background. Most pictures have too many colors and levels. Areas that are too dark will hide dark colored text, and areas that are too light will obscure light color text. Most of the time it make it very difficult to see the web page. But if you know a little HTML, and want try, take a look this link to my Website Wizard Help Page. Item 5 describes a method of adding/changing your web page background. Note that each page will need to be modified separately, and the background of the content areas is handled differently than the overall page background. This means that your content areas will overlay the background image with a different background.
