This idea is from our friends at Hibbard Construction:
Fun and decorative, this is a great way to display your Christmas cards. Use two-inch wide ribbon with the wire in it. Tie a bow at one end and use a push pin or tack to affix the bow to the top of the window frame. Gently pull ribbon taught and using a push pin or tack secure the ribbon to the bottom of the window frame. As your Christmas Cards arrive, use a straight pin or staple to attach the cards to your ribbon.