Transparent window backgrounds for linux, like vista

No, they don't really exist, but I would really like them to... Windows Vista has transparent window borders, but I don't mind, because I can get those with Beryl on Linux. But what about the window backgrounds? Remember Windows Explorer and Windows Media Player? They backgrounds of them, not just the window borders, are transparent.

I think that it is really pretty. I also like being able to drag the window around on the transparent parts. I would love for a new version of KDE or GTK to be able to do these kinds to things. That would be so cool.