Stand to Reason has a collection of excellent Christmas Card Captions, many of them evangelistic and all of them suitable for turning your homemade cards and family letters into good Christmas greetings.
“O God our loving Father, help us rightly to remember the birth of Jesus, that we may share in the song of the angels, the gladness of the shepherds, and the worship of the wise men. May Christmas morning make us happy to be Thy children and Christmas evening bring us to our beds with grateful thoughts, forgiving and forgiven, for Jesus’ sake, amen. —Robert LouisStevenson”
--Stand to Reason: Christmas Card Captions
Be sure to take a look, there's more.