If I could make another suggestion, if would be to allow the selection of multiple files or a whole folder. It's nice to have the logon screen change every time the wallpaper changes, but it would be even nicer to have it change to something different than the current wallpaper.

The way I have it set up now is I have a folder with about 50 wallpapers that are used randomly for each of my monitors after a certain about of time. It would nice if a logon screen could also be randomly selected on a certain time interval too.