>>157228
CSS can be used to change the style, the looks.
BO (Toshaki here on /librejp/) can change it.
/librejp/ already has a custom CSS, different from default Endchan CSS.

The programming side cannot be changed.
But users can use browser addons, such as Greasemonkey, and write a script in JavaScript for that. It will only change things in the browser of that user, but not everyone.

If you need more help, ask on >>>/operate/