I have never done this on my blog and forums, however, on my online stores, I try to use holiday themes in order to improve sales. I even add holiday-related products.
Whenever we come up to a holiday such as Easter, Christmas, and Thanksgiving I will always make an attempt to change up the forum and make it a little more suited for the holiday that is being celebrated. Christmas is my favorite one to change to when that comes round on my forum.
I think we used to on some of the old boards I was a staff member on, but I don't do it to my currently owned forum. I don't think it's too necessary for a resource board. But overall, I guess you can say I'm the Grinch because I'm not very festive.