I decided to do a search to find out the last year that the Madonna Christmas stamps - depicting Mary with the Christ Child - were sold at the post office.
In my first search, I found the following stamp dated 2006:

Description from USPS.com:
Christmas: Chacón Madonna and Child with Bird
The 2006 Christmas stamp features an oil-on-canvas entitled Madonna and Child with Bird. Dating from around 1765, the painting is attributed to Ignacio Chacón-an artist active from about 1745 to 1775 in Cuzco, Peru. It is now part of the Engracia and Frank Barrows Freyer Collection of Peruvian colonial art at the Denver Art Museum. In designing the stamp, art director Michael Osborne slightly cropped the painting's floral "frame" and surrounded the entire composition with a gold border that echoes Chacón's use of gold-leaf embellishments.
A famous painting by Spanish artist Bartolomé Esteban Murillo entitled La Sagrada Familia del Pajarito (The Holy Family of the Little Bird) probably served as an indirect prototype for Chacón's Madonna and Child with Bird. The importance of birds in Inca culture would have made the topic of Murillo's painting particularly resonant in Peru. Birds were sacred to the Inca, partially because of their ability to fly and move closer to Inti, the sun god. So in Cuzco, colonial artists often incorporated birds or feathers into images of the Virgin and Christ to indicate their divine status.
Of course, this stamp is created more for the Catholic religion which believes that Mary was also divine - as was Christ. Unfortunately, that is incorrect. According to the Bible, Mary is NEVER mentioned as "divine." She is properly honored as the mother of Jesus (not "the mother of God") and is called "blessed."
During my second search, I found an article dated back in 2008 at The Telegraph UK which was entitled, "Church leaders fear religious Christmas stamps will be scrapped."
The sub-title tells us why:
Church leaders fear religious Christmas stamps could be scrapped for pantomime designs after Royal Mail forced them to be sold "under the counter".
Take a look at the ugly "pantomime design!" I don't even want to post the photo here at this blog. Well - at least "pantomime sisters" are rightly labeled as "The Ugly Sisters!" Ha! But...c'mon!! What do their ugly faces have to do with Christmas?
I agree with this Canon Chancellor:
Canon Chris Chivers, the Canon Chancellor of Blackburn Cathedral, has called the choice of stamps "utterly demeaning" and said in a letter: "If we are to have Christmas stamps at all, let them be Christian. But if for some mindlessly secularist reason we must have a choice, then let there be stamps of both sorts, in equal number."
Continuing on in my search, I found a blog called Darleen's Place. Her blog archive contains an essay entitled, "US Post Office goes Politically Correct - Updated". She claims that the Mary With the Christ Child stamps were not available in 2005, but correctly speculated that it would be back in 2006 (see stamp above). Lots of great comments there, too.
Darleen's blog led me to a 2005 post entitled, "The War Against Christmas" at Michele Malkin.com. Lots of additional links to explore there, too.
One of the prettiest Christmas stamps I found during my search was from Canada!

Ahhh! I'm running out of time. Hopefully, I can return to the search and find more photos of the Madonna and Christ Child commemorative stamps.
USPS.com Postal History PDF page has listings of all of the Christmas stamps over the years, but no photographs of them. According to that page, the last stamp of this kind issued was in 2009.
4424 Christmas: Madonna and Sleeping Child
by Sassoferrato, by Giovanni Battista
Salvi.
After 17th c. painting by Italian artist
Giovanni Battista Salvi, more commonly
known as Sassoferrato. Hearst Castle,
San Simeon, California.
Oct. 20, 2009 44¢ Carl T. Herrman
It appears that the site hasn't been updated past the date of January, 2010. Perhaps there IS a Mary and Christ Child stamp out there but it's under the counter and customers need to ask for it?
How sad!!!
Darleen was unfortunately correct back in 2005 when she shared:

P.S. After waiting in line and shaking my head about the secularism displayed at the post office, I went to The Family Christian Store and found some beautiful CHRISTIAN themed ornaments!
One is a blue bulb ornament from "The True Meaning of Christmas" line that says, "A Child Is Born" with Isaiah 9:6 NIV on the other side: "For to us a child is born, to us a son is given."
A pretty red bulb ornament says, "Keep Christ In Christmas."
A flat wooden look ornament with a north star design depicts the nativity etched upon it.
A hand painted ceramic heart-shaped design on a dark red background states, "Be still and know that I am God."
The fourth one is in the shape of the cross and has the entire 23rd Psalm written on it!
Psa 23:1 [[A Psalm of David.]] The LORD [is] my shepherd; I shall not want.
Psa 23:2 He maketh me to lie down in green pastures: he leadeth me beside the still waters.
Psa 23:3 He restoreth my soul: he leadeth me in the paths of righteousness for his name's sake.
Psa 23:4 Yea, though I walk through the valley of the shadow of death, I will fear no evil: for thou [art] with me; thy rod and thy staff they comfort me.
Psa 23:5 Thou preparest a table before me in the presence of mine enemies: thou anointest my head with oil; my cup runneth over.
Psa 23:6 Surely goodness and mercy shall follow me all the days of my life: and I will dwell in the house of the LORD for ever.
All so beautiful!
Hat Tips:
USPS.com
The Telegraph UK
Darleen's Place
Michelle Malkin.com