Is it possible to automatically change background image of the lock screen.
For example having it pick a random image from my Pictures
library, or some online source each time it's displayed or maybe changing per day?
Bing My Lockscreen (currently released with more updates coming) is doing exactly this with the Bing Photos.
Bing My Lockscreen allows you to select from the eight most recent Bing images and quickly select which of them to set your lock screen to use.
In addition Bing My Lockscreen allows you to automatically have your lockscreen updated daily with the latest image from Bing - thus ensuring a constant supply of inspiring and interesting new content for you!
Note: This is a submission to the apptivate.ms contest. Help support him and give him a "thumbs up"