Windows 7 offers a specific Aero location themes depending on language and location chosen during installation. But there are many hidden themes from different countries and here is easy tip how to access the other international themes: Just copy and paste the following path into the search box and hit Enter.
In the MCT folder you will find additional themes for Canada, Australia, South Africa, and Great Britain. You can copy wallpapers or full themes by going into the Theme folder and double click on the the thumbnails to add it.
For more Windows 7 themes you can visit official Microsoft page or click here.