Select the desired resolution for the wallpaper, right-click the file that opens in the new window and click 'Save Picture As...' to save the wallpaper.

800 x 600 | 1024 x 768 | 1600 x 1200			800 x 600 | 1024 x 768 | 1600 x 1200
800 x 600 | 1024 x 768 | 1600 x 1200			800 x 600 | 1024 x 768 | 1600 x 1200