So you really like the new Face Movie feature in Picasa 3.8 and want it in Linux too? Well, it doesn't work for now, but you can use PhotoFilmStrip.
PhotoFilmStrip is an application which can create a movie (slideshow) out of photos. It uses the "Ken Burns" effect for the pictures transitions and you can also add music and captions to your photos. The movie can be rendered in VCD, SVCD, DVD or FULL-HD.