The possibilities are endless! Use gel food coloring to change the color or different flavor extracts in the meringue after your stiff peaks form. You can add flavor to the buttercream or add jam, like my Raspberry Rhubarb Jam, in between the cookies. My book Frosted is a great resource if you want to experiment. It has 13 frosting recipes and 60 different ways to customize them and use them in all types of sweets. Search any of my macaron recipes on the site and use those to make them as minis.