For your invitation cut out an array of mittens, snowballs, scarves, snowflakes in your party colors and place all of the pertinent information on the cut outs. Use cookie cutters as guides; they can pull double duty later for craft projects or treats.
Another invitation idea is to paint Styrofoam balls with your party colors, for snowballs, and attach a tag with the party details. These invitations will need to be hand-delivered.