A plot could be about a child writing a Christmas card to Santa, asking for a special gift for his sick sister. The card gets lost on its way to the North Pole but is found by an elf who is touched by the child's selfless request. So, the elf arranges for the gift to be delivered to the sister.
The plot could involve a group of friends who are scattered all over the world. They each make a part of a Christmas card and send it to one person among them. This person then assembles the card, which becomes a beautiful collage of their memories and friendship. It shows how Christmas can bring people together even when they are far apart.
Maybe a story where an artist creates a beautiful Christmas card but loses it in the snow. A kind stranger finds it and is so inspired by the art that he tries to find the artist. After a long search, he finally meets the artist, and they become friends, and the card becomes a symbol of their newfound friendship during Christmas.