Skins 
You can customize Etherpad appearance using skins. A skin is a directory located under static/skins/<skin_name>, with the following contents:
index.js: javascript that will be run in/index.css: stylesheet affecting/pad.js: javascript that will be run in/p/:padidpad.css: stylesheet affecting/p/:padidtimeslider.js: javascript that will be run in/p/:padid/timeslidertimeslider.css: stylesheet affecting/p/:padid/timesliderfavicon.ico: overrides the default faviconrobots.txt: overrides the defaultrobots.txt
You can choose a skin changing the parameter skinName in settings.json.
Since Etherpad 1.7.5, two skins are included:
no-skin: an empty skin, leaving the default Etherpad appearance unchanged, that you can use as guidance to develop your own.colibris: a new, experimental skin, that will become the default in Etherpad 2.0.