A couple of improvement suggestions which can greatly increase the 'wow' factor you might like to consider
1) dynamically fade out the led rather than just setting discrete brightnesses. I recently made a standalone module for adding lighting effects to models and originally coded this up myself. Then I found the SoftPWM library which will do all the fading for you!
2) Use a sine wave calculation to detemine the horizontal position of the light - that way it slows down as it reaches either end of the sweep.
You can see both of these in a video of my prototype board here http://s113.photobucket.com/albums/n202/ants-nest/Misc/?action=view¤t=LEDDriver2.flv