The episode I watched was mostly about taste and ingredients, but there was a theme involved. Each episode has a different theme. For example, this week's theme was, appropriately enough, the Rose Parade. Here's a summary:
Four Cupcake Wars champions set out to prove they're the best of the best as they fight to have their delicious displays featured at the coronation of the 2011 Rose Queen, as well as the special grand prize of being featured in the internationally renowned Rose Parade.