I like the idea of a book at the top of the cake with the cap on it. You could play around with round and square cake shapes.
How to make Sugar Paste Fondant Graduation Caps & Diplomas - Cake Toppers, Cake Decorating, Tutorial, Sugarcraft, Sugarart, Fondant Icing | happyfoodstube.com
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Graduation Party Cake
Its a cake tat i can make for my daughter on her last day to school. It looks so pretty.
Learn how to make easy GRADUATION DIPLOMA CUPCAKES with fondant. Perfect for graduation parties. These graduation cupcakes will make you believe in easy cake decorating. From http://cakewhiz.com
This is the cake! Library cake. Will do all the book spines well in advance, then just stick them on at the last minute.