Bithaus has a handy little chunk of Objective C source code up that provides programmatic capabilities to styling NSWindows. It’s modeled on Matt Gemmell’s snazzy TunesWindow class (which I use in iRooster, by the by), but appears to handle all of its window style in code instead of by loading and stretching PNGs, as TunesWindow does. Very cool, very handy.
I imagine that I will incorporate this into iRooster before too long. It’ll be nice to get rid of the few little PNG files that I have sitting around to draw window backgrounds, and also I should be able to provide some sort of power user feature for customizing the window background. I’ve always enjoyed providing fun, little undocumented features like that in my app.