Here is how you do it:
1. Click Start, type in: C:\Windows\Globalization\MCT
and press Enter.
2. You will now see 5 folders
(MCT-AU, MCT-CA, MCT-GB, MCT-US and MCT-ZA)
3. You can go into those folders and press the folder with the country
name to find wallpapers or you can press the "Theme" in order to
activate the theme
Video tutorial