This question is a bit more general but I like photo SE's design the most. There are many 'default'-styled (not ugly but a bit unreadable and too uniform) beta SE sites out there. That made me wonder, just who is allowed to control a SE sites looks and exactly how it is done?
Photo SE also features a photo of the week in the header, how is this functionality put into the site's code?
UPDATE 1 Who is capable of changing the default looks of an SE site and how does he do it?