I'm not changing it this year - we have too much going on right now. (We're moving house the week of Christmas!) But last year, I recolored my template images to Christmassey colors and I added a Santa hat to the cartoon me in the header image, and added a silhouette of a Christmas tree to the silhouettes of my kids. It came out pretty cute, I thought. Still looked the same as every, except festive for Christmas!
I don't have the time to change the design so I've opted to dress up my blog a bit with a picture of the Eiffel Tower trimmed in garland and Christmas lights.
In fact, I don't plan on changing my banner in the near future, but I will keep the corner changing with interesting Eiffel Tower pictures to mix things up a bit.
You can see it here under "My Favorite Paris Landmark":