In The Magician's Nephew, Digory and Polly (along with a couple others) have the very unique opportunity to witness to creation of an entire world. When they arrive in this world, initially everything is dark, not like the lights are out, but like there are no lights at all. Then the stars start to shine and then the sun rises. They hear a song, a beautiful song. It is from this song that everything is created, and this song is sung by Aslan himself. After seeing the connection between the Lion's song and the creation of things, Polly thought that all of these things must be coming "out of the Lion's head."
As the creator of Narnia, Aslan was an artist. As the Creator of our world, God is also an artist. He creates wonderful and beautiful artwork. It is only by the hands of men that this beauty has been destroyed...or rather deformed. We have changed the world from the beautiful thing it was into what it now is. Still beautiful, but not as God created it. one day, however, we will get to see the New Heaven and New Earth in all of its beauty, but I'll save that for another time.