My oldest son recently turned 12. For his birthday he asked that everything be galaxy themed. I had already spent a lot of time watching videos of galaxy mirror cakes and knew that it wasn't something I wanted to try out for the first time on his birthday cake. So, I decided to pipe little puffs of galaxy clouds on to the cake instead.
I used blue, purple, and pink icing to make all of the cloud puffs, and then I added black sprinkles with gold and neon blue edible glitter, and some edible stars. He absolutely loved it and I actually had a lot of fun throwing glitter at the cake.