Help creating slideshow effect

Hi, perhaps someone can help me:
I am trying to create a full-frame photo slideshow/photo transition like the one on this site–

It shows a random background photo each time a link is clicked and has a nice diagonal “wipe” effect for a transition. Then photos of their work are shown when exploring that section. How would I generate the random photos and transition effect upon clicking a link?
Does anyone know of a similar tutorial?