Unfortunately since SpinWall is subscription based, if it had the ability to operate in an offline mode, there would be no way to validate if an account is active or not (or when the trial expires). Beyond that, there are plenty of simple wallpaper rotators, however the advantage of SpinWall is it allows the user to change their background between the many thousands of images on Desktop Nexus, without using much hard-drive space (only a few megs), since everything is retained on our site rather than your computer.