Australian here. Christmas decorations will go up shortly for a lot of people. They come down a day or two after Christmas.

Obviously the main difference is that it’ll be the middle of summer so it’ll be unpleasantly hot. A lot of people do BBQs for a shared meal, seafood is a very common thing here for Christmas, especially prawns. Oh and Cherries. Everyone loves cherries for Christmas for some reason. And Pavlova

Other than that, it’s probably pretty similar to Christmas in the U.S.