Christmas cards were given at Christmas time.
According to Santa Claus, his "mugshot" was on every Christmas card. (TV: Last Christmas [+]Steven Moffat, Doctor Who Christmas Special 2014 (BBC One, 2014).)
In 1972, the Twelfth Doctor helped Jess Collins deliver Christmas cards to various friends of the Collins family. (COMIC: Be Forgot [+]Error: Code 2 - no data stored in variables, cache or SMW.)
In 1992, Chad Boyle mailed Christmas cards to all of his old friends from Perivale. (PROSE: Love and War [+]Paul Cornell, Virgin New Adventures (Virgin Books, 1992).)
In 2017, Erimem wrote Adam Docherty a Christmas card which said, "May your enemies drown in their own blood". (PROSE: Message in the Cards [+]Error: Code 2 - no data stored in variables, cache or SMW.)
Received cards were typically hung up on display. (TV: The Christmas Invasion [+]Russell T Davies, Doctor Who Christmas special (BBC One, 2005)., The End of Time [+]Russell T Davies, Doctor Who Christmas Special 2009 and New Year Special 2010 (BBC One, 2009-2010)., Last Christmas [+]Steven Moffat, Doctor Who Christmas Special 2014 (BBC One, 2014).)