Wood R4 uses Acekard 2 skins. And to use them, inside the _rpg folder there is a folder called ui. In there, each skin has it's own folder, called whatever you want (just don't make the name really long). A good place to download skins/themes is http://www.ndsthemes.com/
(just make sure you get Acekard 2 ones).
When you download one from there, on the details page for each skin there is a note about putting some of the files in a calendar folder to make the calendar work. Just read that note and do what it says (it's just below the screenshot of the skin).