I've spent some hours on google today looking on how in the hell to theme os x leopard, but I've found nothing. I'm wondering how it's done, if it's done? Also the transparent bar is pretty gnarley, I think I've seen that around.
The tools for themeing leopard arent quite released out of the beta stage. But there is a cool theme. iLeopard it is what I use, basically it uses the iTunes style everywhere, it is much nicer looking than aqua.
There was supposed to be a themeing app called Facade which had a great number of feature, but seems to have gone into limbo. Another themeing app that exists is called Magnifique, it's somewhat buggy though, it uses AppleScript to do the work.