A custom userChrome.css and userContent.css that rounds corners, and enables users to add a background to the default Firefox newtab page. This image is defined as image.png in the /image directory. I also enable use of a custom font in the Firefox UI. I use Poppins, which I will not distribute in this repository in respect to its creator, Indian Type Foundry. You may install any font you like within the /fonts directory, and you will need to edit line 4 in userChrome.css and line 6 in userContent.css accordingly.
NOTE: This userchrome.css is currently (partially) incompatible with the new sidebar tabs on Firefox, as the CSS selectors for both are the same. Zen also does make many of the same changes, but better.