Carrousel effect for multiple login screen background images

On the OO10 loginscreen we have a great wallpaper background image. Of course, one image is not enough, so we need some carrousel effect as seen on the twitter homepage.

The goal is to make a little ooBgCarrousel jQuery plugin that can be used by the theme.js to implement this feature. The functionality is not limited to the login screen.

As an example usage the effect is implemented in the openolat theme.