It can be downloaded directly from this location:
Windows 7 Box Art Themes
In the .zip file you can find four themes.
To visit Windows 7 Box Art Theme website follow this link:
Theme called Windows 7 Ultimate.themepack and that is the theme shown above.
Instructions on how to install the themes
1. Unzip the files from downloaded .zip file
2. Double click on the file named Windows 7 Ultimate.themepack to install the theme.
3. Right click on the desktop and click on the option Personalize and select the theme that you have installed