Well, it's not christmas at my house until we have brownies. and, you could make them different by serving them with chilled egg nog sauce drizzled on top.
The warm brownie with the chilled sauce would be super good.
And if you want to be more fancy and festive. first pour some sauce on the bottom on the serving plate, add 1 or 2 dots of red and green food coloring and swirl into a decorative design to give it a definite christmas feel.
Here's a recipe for the sauce Traditional Egg Nog Sauce Recipe | Recipezaar