Multiple stripes of different colors of crackle polish with the top layer being a full coat of black crackle. The same effect could be achieved by using regular polishes to do stripes on the nail then topping off with the black crackle.
No, I am not recommending neon nails for your wedding, but the idea of being able to do color gradations on your nails with gel polish is intriguing. Imagine using pale blue, fading to grey and then pale pink. very pretty and unique.