Something funky would be cool, something with geometric shapes or stripes! Really depends on what she likes!
Go to cake websites for some ideas. Here is one: http://www.edibleartbakery.com/Default.aspx?tabid=42 There's all kinds of ideas you can get from different cake sites. Good luck and hope she has a wonderful time. Stephanie--mom to 7
Who is going to make it Are you going to make it or have it made? It also depends on what all she is into which kind of decides what should go on the cake. You said that she likes art. For drawing (art) pencils and such, for painting you could use tinted buttercream in the form of brushes and bottles of paint.