What type of design should I get on my cake?

I'm 16 and am odering a cookie cake from a local grocery store. I'm ordering it this weekend, but I still do not know what type of design to put on there. I know I want purple included in it because that's my favorite color. And I was thinking of having like a small chandelier or something, but then I was wondering if they could draw/ create it. Can anyone give me any ideas? Thanks.