WE had a princess themed party for my niece. As I was hanging the streamers, I noticed the box for our new dresser. The model name for our new dresser was 'castle.' I got an idea; I used purple acrylic paint on the sides, plastic ties to secure the top flaps (Not closed, but sticking up), and panted them gray. Then I repainted the top flaps using special 'rock' spray paint. I trimmed the line between the purple/gray with yellow construction paper, and cut and trimmed a door. Last, I made two towers using streamers and construction paper cones. IT looked great, and the kids had a blast! Overall, it was pretty easy to make. I watered down the paint, so it wasn't very expensive at all.
I also made a pastel colored sheet cake (white frosting, pastel trim). Michael's Crafts had this amazing purple cake 'glitter' that looks great. I also used cookie cutters to make designs which I then traced with gel icing from a tube. It was pretty easy, and made a great looking cake!