we'll i am 11 year old girl and im inlove with one direction, so for my birthday cake i got a picture of one direction printed on my cake with edible ink and paper on the second tier, for the first tier i made figures from gum paste (you can use fondant or marzipan) of the members of one direction it looked awesome! but you could do this with any band or singer that could work quite well with justin bieber, you could also make a collage of pictures of that singer or band! also zebra prints was a fantastic idea! if you want to add a twist to the zebra print idea you could use your favourite color as the background for example i really like they color green so i would do a green background maybe then black zebra stripes (but you could use your fave color!) i also think pink would look awesome! if you have a theme for the party then you could carry the theme into the ccake like if the theme was hollywood then you could made movie strips and a camera a directers secne clip things a red carpet an award.......?
i really hoped this helped!