Place egg whites in a medium bowl. Let stand at room temperature for 30 minutes. Preheat oven to 300 degrees F. Line two very large baking sheets with parchment paper or foil; set aside.
Add vanilla, cream of tartar, and salt to egg whites. Beat with an electric mixer on medium speed until soft peaks form (tips curl). Gradually add sugar, 1 tablespoon at a time, beating on high speed until stiff peaks form (tips stand straight) and sugar is nearly dissolved.
Transfer meringue to a decorating bag fitted with a 1/2-inch round tip. Pipe teardrop mice shapes 2 inches apart onto the prepared baking sheets by piping small ovals about 1 inch in diameter, with one pointed end (for the face).
Bake all of the meringue mice at the same time on separate oven racks for 5 minutes. Turn off oven; let meringues dry in oven with door closed for 1 hour. Lift meringues off paper or foil. Transfer to wire racks; cool completely.
To decorate each mouse, use the tip of a small sharp knife to carefully cut two small slits on top of each head for ears. Insert an almond slice into each slit. Use a toothpick to make a small hole about 1 inch deep in back of each body for tail. Insert a piece of licorice into opening. Add two small dots of decorating gel for eyes and one dot for nose. Makes about 72 meringue mice.