We see more and more downloads each day on Christmas images, so if you plan to have Christmas in your portfolio, it is now that you need to upload. In fact you can consider you are already late and really hurry. Designers are already downloading images and sending them to the client for review. Don't wait for the Christmas to arrive, very few will actually download them at that time and the selection criteria will be tougher. You might want to do a careful search before uploading, remember this is the most prolific theme of the year, so don't upload the same cliches.
Read Petar's new article for more hints on Christmas and stock photography.