Once you've mastered the basic techniques, you can really start to play around with your "peeps."
Vanilla flavoring can be substituted with another flavoring, such as almond, mint or lemon extract. Or you can use powdered spices such as ground cinnamon. You can even use rose- or orange blossom water, which is actually quite delicious. Start by beating in about one-fourth teaspoon of the flavoring at a time and then adding more to reach the desired taste.
Colored sugars are available at most grocery stores as well as at cooking and baking supply stores, but you can make your own custom hues: Place granulated sugar in a sealable plastic bag or jar with a few drops of food coloring, then shake until the coloring is evenly distributed. Spread the sugar out onto a rimmed baking sheet for about 30 minutes to dry, then sift the sugar before using to remove any lumps.