Just an 8chan theme based on Tomorrow
Simply put 8chan-tomorrow.css content in your custom CSS or @import url("https://rawgit.com/7185/8chan-tomorrow/master/tomorrow.css"); if you want to try the latest version (not recommended because longer loading times, but fine for a quick preview).
Remember to keep the default theme selected (Yotsuba B) in order to avoid conflicts with other themes. If that bothers you, have a look at my userscripts repo and use same-css-everywhere.js to completely ignore other themes.
Feel free to suggest anything.