Apparently, the Emerald window decorator, which runs with the [Compiz window manager] (somehow I get the feeling that "runs" is not the correct word to use here), offers many fantastic-looking themes to the desktop. However, its ppa is not included (though the default repositories contain Compiz somewhere) and it must be manually added before it can be
sudo apt-get installed.
Compiz's documentation on it is a bit spotty, but then again, a lot of Compiz's documentation seems a bit incomplete (as in, there are section headers that have no content beneath them). Is Emerald still actively developed to keep up with new OS releases, or will there be performance losses/quirks due to slight incompatibility? It looks great; I just don't want to use it if it won't work 100% correctly.