“Merry Christmas” or “Happy Holidays”?
“Seasons Greetings”? “Cool Yule”?
Maybe “Marked Down—5 Shopping Days Left!” would capture the meaning of Xmas. But if you're a traditionalist, here is the best way to say you've got that old-time spirit of the season.
As an added bonus, “Merry Saturnalia” might make a wingnut’s head explode.