If you've used Windows Phone 8, you may have come across the ability of Bing and Facebook to automatically change your lock screen wallpaper. With this new ability in Windows Phone 8, expect to see more and more apps take advantage of this. One early example is Astronomy Lock Screen. This simple app takes the daily image from NASA's venerable website, Astronomy Picture of the Day (APOD), and sets it as your lock screen wallpaper. There are no settings as such, but the app can download the image to your gallery and take you to the corresponding APOD page for the image.

While Bing always provides visually interesting images, this is great if you like to admire the cosmos more than places on Terra Firma. Best of all, the application is free of charge too.