Celebrate the U.S. Independence Day in style. This free Patriotic Windows 7 theme pack gives you three very attractive and artistic wallpapers, featuring a colorful drawing of the American flag, a beautifully rendered Declaration of Independence, and an abstract stars-and-stripes graphic. Very nice. The only other changes to your interface are a pleasant sounds package ("Garden") and blue window treatments.
The theme is very easy to install: Just double-click the themepack file once you've unzipped it.