I love this idea so I
did some mockups:
Desktop
Dash
Window Theme
Indicator Menu
I recommend downloading the attachments and viewing them
fullscreen to get a real idea.
The window theme and the indicator menu are not transparent,
but I don't think they need to be either. In this particular
case transparency adds graphical requirement without
achieving a great deal IMHO. I think that an opaque theme
which dynamically matches the background colour would work
just as well.
Thoughts?