Hello Friends
	There is a trial version available and the full version is available for $0.99, we are not sure what the limitations of the trial version are.

Hello Friends lets you decorates your lock screen with collages of your friends. The app comes with many different templates and you can pick one and the app will automatically change the wallpaper with new friends from time to time. You can change the refresh time interval and the app will pull up images of your contacts and put up a pretty collage of your friends. So if you are not a fan of the traditional Windows Phone Wallpapers and want to have an app that will automatically update your lock screen.

The latest updates adds some new features like adjustable refresh time interval , only allow specific contacts to be used in the collage, etc. Currently the app only works on Windows Phone 8.