This is just a handy tip a bit of a tweak
When you install win7 it will ask for a language choice and location. This is where win7 decides your default themes. Hence if you are in the USA you will have desktop backgrounds of Oregon,Maine etc. However you can access the other locations quickly and simply by just typing
C:\Windows\Globalization\MCT in the search box. Note that you may need to change the drive letter depending on where win7 is installed on your PC.
Now you should be in the MCT folder and see 5 folders
MCT-AU = Australia
MCT-CA = Canada
MCT-GB = UK
MCT-US = USA
MCT- ZA = South Africa
From here you can go into each folder and grab whichever background takes your fancy or add whichever theme you want to "MY THEMES".
Enjoy