Size of the Universe

Mike sends along a video of writer Francis Chan giving us a visual illustration of how vast our solar system, our galaxy and the universe are. It's literally awesome:

Here are some homework questions: In the last scene, a view of the entire universe, what's the black region outside the mass of galaxies that makes up the universe? It can't be space because space is a property of the universe. Is there really anything there or is there nothing? If the latter, what exactly is nothing? Does it go on forever?