Honestly the TS we have been to have had some decorations but they have all been pretty similar nothing really has stood out. We love to resort hop to the different deluxe resorts they do an amazing job with decorations and we really like Epcot and MK. I heard they had more at DHS last year so can’t comment and previously have not had much at AK.
I agree with CynBeth. They are all, pretty much, generically decorated for Christmas. I would suggest, perhaps, dining at one of the restaurants at WL or GF as the decorations, overall, at those resorts are off the charts, so you definitely get more of a Christmas feeling there.
I think the little squares within Epcot were the most "Christmasy" in overall feel. Several restaurants over look them so pull out your maps and then pick the cuisine that fits your wants.