Yeah, by adding themes to the theme drop down you provide a skin for everyone using the web wallet you've customized. We've only really got 5 or 6 themes (several exclusive skins to rudex/openledger/btsabc), we should have many skins like you see in IRC/Text clients! :)

It needs node.js v6 (not tested v7) and nvm, if you have those on windows then I don't see why not!