'Fine art handling' firm, Momart, issue artists to create a greetings card each year. I found some examples on the V&A 'Search Collections' site, and I must say I was amused.
Here are some examples..
Tracy Emin, 1999, a napkin with 'stay faithful to your dreams- Tracy Emin' written on it.
Tim Head, 1987, an abstraction of a common Christmas motif, enhanced with the use of flock. Sir Anthony Caro, 1993 and his bronze belt buckle cast.
Richard Deacon, 1996, Draws amoeba like forms for his festive commission
Damien Hirst, 1997 uses his signature circles, which have been screenprinted onto perspex.
My personal favourite is Langlands and Bell, 1998 and their watched named frozen sky, which displays 25 three-letter international airport abreviations on its face.
More Christmas musings here