We were there during the holiday season a couple years ago. Pictures are in link in my siggy.
For Fort Wilderness, I loved seeing how people decorated their cabins and golf carts.
At each park there is a Christmas tree with the theme of the park. Make sure you see all of those and get pix!
The Osborne Lights at Hollywood Studios was AMAZING!!!! Again, see my pix!
The Christmas parade (extra $$) was OK. I didn't love it but I'm not a huge parade person to begin with. See pix!
I feel like there was a special thing with the Castle in MK at night. I can't remember if that was part of the Christmas parade or not. They projected all kinds of different images on it and it was amazing (pix below!)!!! I don't remember that from the first time we went in August. Maybe someone can correct me..