Originally Posted by Baldilocks
Check my siggy for wallpapers for the GS III.
1440 x 1280 is the correct size (if you use scrolling wallpaper.)
Since this link also comes up when Google searching this issue, I will correct this misinformation here as well.
Make your image 1280x1280 NOT 1440x1280. If fits perfectly. The cropper has a predefined proportion. It is square.
If you have a 1440x1280 wallpaper it will still work, you'll just have a little bit of the left and right edges of the image cropped out.
Look at your GS3 default wallpapers that come with the phone. They are all perfect square images. And when you pick an image to make it your wallpaper, notice the cropper is a perfect square. It is not some wide proportion made for 1440x1280.