If you download the Nokia Collection app ($1) from the Windows Phone store you get a link to an app called Glance Background. I can't find this in the store by searching so it looks like you have to go through the Nokia app unfortunately.
Glance Background does what it sounds like it should do. It lets you select a picture to display on your Glance screen (Nokia phones only). There's some rudimentary editing effects you can perform on the picture first and it lets you rotate up to four different pictures.
The final effect on your phone can look very cool and it's worth the $1 you have to pay to get access to it.