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.
rr Drop a few drops of a neon polish in a disposable cup of room temperature water. Spray some perfume, hairspray, or hand sanitizer on top of the colour. It will create little lines of your chosen colour! Dip your finger in, and repeat with more colours!