I don't write PBs, but I'm glad to hear stories like Cynthia's that show it's possible to sell a holiday story as a new author/illustrator. It seems most of the ones in the stores have been about tried-and-true characters (Olivia the Pig, Judy Moody), or by big-name illustrators, or perennial favorites, or books generated by the house or a packager. I'd love to see the holiday offerings get broader. I agree that kids will read a holiday story at any time of year, and for that matter, a summer story in the winter, etc. So will I!
Years ago, a friend of mine got into children's writing b/c she was a kindergarten teacher who was frustrated with libraries' "one holiday book per child" rule. She felt this meant not enough of them were being published. She never sold a holiday story, though did sell in PB NF. I think you all are right that you really need that special angle. Love the general encouragement in this thread!