[xmonad] Gaps between windows

[Damian]

(or in winter I need some color...)

Hello,

I want to configure xmonad so that it leaves some amount of space
between windows. Here is a mockup:
    http://yfrog.com/1glayoutiwantp

The closest layout I could find is XMonad.Layout.Gaps, but it does not
leave space between windows, it introduces a gap with regard to the
screen.

Any ideas about how to get this behaviour?

Thanks in advance,
Damian.