I recommend this one, it's great! [+]LockScreen | Windows Phone Apps+Games Store (United States)
[+]LockScreen
It's a free version to, but I really recommend buying it. It has some nice features, like visualizing the lock screen clock, date and notification while you look through the backgrounds.
Just wanted to share my lock screen photos with you, you can download them here: https://skydrive.live.com/pagenotfounderror
I also use Paper Shuffle to set the photos I like and the program changes the lock screen every hour Paper Shuffle | Windows Phone Apps+Games Store (United States)
i allow tvshow to handle that.