this theme is the best theme available, contrast and usability is just perfect! but only if your monitor is not bigger than 1920 width though.

i edited the file to fit bigger resolutions, not sure about making it public, don't want to run into copyright troubles.

basically just open the file (google how please), scale the image to 5k, delete meta inf folder, save as zip and release as private in developer page. you get a link from mozilla to install it.