OK, I've been using XFCE for almost two years now (and loving it more and more).
So I'll just give a rundown on what you're installing and where to "see" it.
First off, there's a Window Decoration theme. This theme affects how your X windows look. In a default XFCE installation, the Window Decoration themes are located at
/usr/share/xfwm4/themes.
Secondly, there are User Interface themes. These themes affect how your panels, buttons and other UI gadgets look and behave. They are also known as
GTK themes, and are used in Gnome (and probably other GTK based DEs) as well. They are located at
/usr/share/themes.
How to tell which is which? Well GTK themes usually contain directories called
gtk/ and
gtk-2.0/ in them. The should also contain an
index.theme.
XFCE window decoration themes contain lots of
*.xpm and
*.svg images which form the look of the window decoration. The file names are also descriptive, ie.: bottom-right-active.xpm, bottom-right-inactive.xpm, close-active.xpm, close-inactive.xpm, etc.
Hope this helps
