The tutorial is from the point of view of Technostar.
Now, you start off with your own marble skin. I am using an official MBP skin for this. Here it is:
If your skin is a square, you can skip this part. If not, use a basic image editing program (normally pre-installed, but not paint) to resize it into a square.
Here is the example:
Now, use Gimp 2.6's spinning globe animation (filters/animation/spinning globe) and set the number of frames to 90. It will take a minute to load, so be patient. Now, save it as a .gif file and allow animation. Set the frame rate to 10 milliseconds. Now, you have an animated marble you can upload to the forums!
My final result: