If you asked an Italian what clothes they usually wear at Christmas, their answer would probably be 'the same clothes I wear the rest of the year round.' And this would be the most accurate answer.
Whilst there might be an emphasis on dressing in a particular way for family gatherings and important meals, this would usually constitute nothing more than putting on a smart jumper or switching sneakers or tennis shoes for those loafers that are gathering dust in the cupboard.
Foreign influence on Italian Christmas celebrations
The main overseas influence on the way Italians celebrate Christmas can probably be attributed to the wealth of American movies and products that are developed specially with the festive season in mind.
Because of this influence, foreign imports that you will now commonly see in Italy range from the use of Christmas lights through to Reindeer-emblazoned knitwear.
Italian Christmas traditions
Italy does, however, have a few traditions related to Christmas that may be of interest to you. For me, the most significant cultural difference is that Italians view the main Christmas period as starting from the 24th of December and lasting till the 6th of January, or from Christmas Eve through to Epiphany. This is in contrast to many countries that are returning the tree to the attic and nursing hangovers by Boxing Day.
Another marked contrast of the Italian Christmas is that many children have to wait until January the 6th till they receive any presents. This isn't so much to do with delays in Santa's schedule, and more to do with his job being taken over by an old witch!
In Italy, children receive gifts on the day of the Epiphany, which is when the three wise men arrived at Jesus' manger bearing gifts. And whilst Santa Claus is still a recognizable figure to Italian children, traditional Italian Christmas tales speak of a witch called La Befana who the wise men met on their way to visit the baby Jesus, and who is now responsible for filling the stockings of good children with toys and sweets.