They have all been similar base beers ... a malty winter warmer ... with various flavorings.
I've used Smoked malt, Peppermint, Peanut Butter, Cherry Pomegranate, and other flavorings.
If you're interested, there are links to every single recipe on X-Mas Ales 2009 - 2023.
Towards the beginning of 2023, I realized that I had not brewed beers in every category of the 2021 BJCP Guidelines (see Sheppy's Blog: I lied), and I thought that Category 33 - Wood Beer would make a good X-Mas Ale.