Does anyone have cake decorating ideas for an 18th birthday?

okay. i made this AWESOME cake once. it needs to be like yellow cake or white batter though. take bowls and poor the same amount of the batter into each. put different color food dye into each. mix it. then but it plastic bags, and cut the tip off. you can put it in different designs. you could do stripes, layers of different colors, or just go crazy and make it like a marble type. (i did the marble) and then bake how you would :) it comes out super crazy tye dye like it's really cool :) i thought it might make a gross color, but if you cook right away it's fine :D good luck and happy birthday to her :)