Dress it Up:
Add a cream cheese or cheesecake layer! For cream cheese layer, simply soften 8 oz cream cheese and add about 1/4 cup powdered sugar. Stir together until blended, and spread over bottom layer of shortbread crust before topping with blueberries. For a cheesecakey layer, also mix in an egg to the cream cheese and powdered sugar mixture before spreading!
Change it Up:
How about some different fruit options? Raspberry, blackberry, peach, strawberry, or a combo like peach-blueberry. YUMMMMMM!