Feature request: animated wallpapers and wallpaper improvements

1. I'd be awesome if we could use a video files (.mp4 or something else) for wallpapers instead of static images. As I discovered from my small project, the animated wallpapers should be implemented directly in xfdesktop so they would be drawn before desktop icons. I think we should use gstreamer for fast video decoding which can be integrated with GTK 3.

2. I think that static wallpaper should optionally have a fading animation between wallpaper changes. Is it possible to do this in libcairo?

KDE has this features if I remember correctly. Thoughts?