I also added a fun "extra festive" mode that enhances the festivity level of the site beyond it's normal look. I love it, but I expect it to be controversial :-D
It's pretty easy to `git clone` and install it (instructions for Firefox and Chrome in the README.md). I haven't put it in the extension stores as I have no idea if anybody else would want it, but if it turns out there are dozens of us[1] that want to use it, I will do so.
Goal is to fully support Firefox and Chrome (as I'm a Firefox user primarily), though I haven't found a way to get the Christmas tree animated gif to load in Firefox so that one part doesn't currently work. I tried all kinds of hacks to convert the tree into an animated svg, and even generate new ones, and they are laughably horrible. I'll continue to look and try stuff but for now at least it will just display the alt text on Firefox.
Settings are accessible by clicking on the extension in the menu or tray.
[1]: A nod to the iconic Dr. Tobias Fünke from Arrested Development