I think the coolest part of the picture is that you can see the camera in the marble... It's real easy to see in the bigger version of the picture. Kudos to the photographer for capturing a different view of himself as well.
I always noticed their beauty. As a kid, I used to like them over what other little boys played with, lie action figures and toy cars, I liked my marbles to the point where 'd get soo depressed if one got chipped or cracked, since its beauty would be tainted.
I always loved spinning them on the desk, and watching their patterns change