Don't shoot the messanger, but.. the light version cannot be done with Maemo 5 in it's current state. Mostly because of how Maemo 5 UI handles the fonts and font colors. I think those "screenies" are just photoshop mockups and they're asking help on how to actually turn those into working themes. I actually started to draw a look-a-like of the light mech theme, but gave up since the light based themes just does not work with many built-in closed source apps (thanks to Nokia who hard coded white fonts here and there).