This picture is special because it exploits a Commodore 128 bug (it's a feature!).
(ed.CONS:removed wrong info in accordance with lanch.)

How does this feature affect the picture, Lanch ?

I don't want to write incorrect info, AFAIK it's a trick on VDC (see http://en.wikipedia.org/wiki/MOS_Technology_8563 ) the additional C128-only graphic chip operating next to VIC II, the picture features more shades of greys than would be normally possible. The trick itself was hard or impossible to reproduce on emulators at the time of the demo release. I'll try to dig online more info but authors' speech would be best.

the pic is done as usual ifli, would be displayable on a c64 either. the colors shown here are not the same shown in the demo, which use a brown to yellow scale. also the graphics in the fli bug are missing in this shot.