Reddit mentions of Merry Mixmas

Well you've already got my favourite one :P but for the sake of variety, try some of these (not all of them are ALL jazz, but I would say they're all 'jazzy'):

Baby it's Cold Outside

Boogie Woogie Christmas

Christmas with the Rat Pack

Have Yourself a Jazzy Little Christmas

A Jazz Christmas

Jazz for Joy: A Verve Christmas Album

Jazz to the World: A Christmas Collection

Merry Mixmas (one of my other favorites - most of them are originally jazzy, but were remixed)

EDIT: Formatting.

From the album, Merry Mixmas:

 

(Everybody's Waitin' For) The Man With The Bag (Thunderball Mix)


 

Have Yourself A Merry Little Christmas (Away Team Remix)


 

And the fat man's comin' in hot with Santa Claus Is Comin' To Town (Johnny Mercer), although I always like to pretend it actually say's "Batman's coming"

If you need to keep it proper.. I really like Merry Mixmas - Christmas Classics Remixed .. standard songs.. little twist

You could try this, its all good remixes of classic songs.
Amazon link