Here are a few things that I think would be different:
Carols by Candlelight
As Christmas in Australia is usually characterised by sweltering heat what better way to celebrate the occasion by gathering in a park after dark and singing along to Christmas carols? This happens all over the country from small local productions to massive crowds like the photo above. Popular with families and young children the night includes guest singers and fireworks at the end. I imagine if this was done in the northern hemisphere you would all freeze your little butts off!
Cold Meats and Pavlova
Another weather orientated tradition. Because it's so freaken hot outside there no chance that we'll be cooking a hot roast for Christmas lunch/dinner. Instead we have cold meats like ham and chicken and seafood, accompanied by salads and bread rolls. Best of all, dessert is pavlova. A fluffy meringue full of sugary goodness with fruits and cream. Doesn't matter how much food you've eaten, there's always room for pav!
Simple tradition, but one of my favourites. When everyone sits down to Christmas lunch or dinner, they take a Christmas cracker (or bon-bon) and pull it apart. The one who gets the large end gets the prize. Usually some useless figurine, a lame joke and a paper king's hat. It is very normal to see everyone having lunch all wearing these paper hats. Maybe not the dog though (just an excuse to post a cute puppy photo).
Boxing Day Cricket
After an exhausting day of dividing yourself between multiple family events on Christmas Day, there's nothing better than spending Boxing Day (26th December) getting up late, eating left over Christmas food, putting your feet up and watching the Boxing Day test match. Doesn't matter if you like cricket or not, this is what you do.
I'd be interested to hear what others do over the holiday season . . . .