Well, I usually use Blue, but upon reading this thread I decided to try out Graphite for a while, becuase I have Uno installed, and I thought it might go along with the whole simplistic thing. I'll probably switch back to Blue soon though, as Graphite is a little boring. What other sorts of appearance types would you like to see? I think orange might look ok, but other than that, I can't really think of any color that would look good. Or are you talking more about giving built-in OS options similar to the themes Shapeshifter offers?