Austria issued two different "Christmas greeting stamp" designs in 1937. However, there is some debate as to whether this is actually the first Christmas stamp.
The Austrian stamp designs both have an image of a rose in a vase at the center bordered by the 12 zodiac signs on either side. The smaller denomination stamps (12 groschen) have a green color, however, while the larger denomination (24 groschen) is red. There is some debate that a stamp issued in 1898 by Canada that bears the inscription "Xmas 1898" is the first Christmas stamp, but the stamp does not otherwise have a Christmas theme other than the inscription.