I had made quite a few when i found out about them.
I made my Darkrai one with the black hearts that swirl around, it looked pretty neat.
When I was completing the elite four, I had my Luxray with the black smoke that rises upwards, and the thunderbolts that shoot downwards set just above the smoke. It looked like a big thundercloud forming and shooting thunderbolts everywhere. Definitely one of my favorites.
The others weren't cool enough for me to remember, I guess.