Windows 7 has some eye candy themes by default. However, you can also install themes from around the web and enjoy a new look to your Windows 7 desktop. LIFE theme is official theme released by Windows and they have done a good job of making it really good looking with some fabulous wallpapers. The theme has 5 fabulous wallpapers and is only 4.6 MB in size.
You can download LIFE Windows 7 theme for free and can start using it.