The cookie you decorate is something to have fun with. Remember, there are many backups in case you mess up while decorating. Again, be creative and have fun with this. You can use sprinkles, food coloring, icing, whatever you want.
I like to use sprinkles, and every once in a while, I will use chocolate chips or some cinnamon to spice things up for the holidays! The possibilities are endless, but the most important part is to have fun with this!