The great thing about this simple recipe is that you can mix and match your flavors based on your personal preference and what you have available. Fresh mint, strawberries, chopped walnuts, and even red onion all pair well with the other ingredients in this watermelon blueberry feta salad. Go ahead and experiment to create your favorite combination! Or, mix up your watermelon blueberry feta salad without the greens and add freshly chopped basil or mint instead.