As we learned in tip 4271, a customized desktop them is stored as <ThemeName>.theme in your My Documents folder.
Built-in themes are stored at %SystemRoot%\Resources\Themes.
You can send a .theme file in an e-mail, or copy it across the network.
The recipient should:
1. Right-click the desktop and press Properties.
2. Select the Themes tab.
3. Select Browse in the Theme drop-down box.
4. Browse to and select .theme file.
5. Press OK to load it.
6. Press Save As and Save to save it in their My Documents folder.
7. Press Apply and OK.
NOTE: If you copy the file to the users My Documents folder, they can simply select it in the Theme drop-down box, pressing Apply and OK.