Very unique and ambitious tileset Elimnator. Monochrome themes can be a difficult medium to work with - especially for video games. US filmmakers, during the 1940's, didn't have the luxury of using color film stock on every studio film production but they had one clear advantage over modern indie game designers -the innovative use of lighting. The result was film noir productions - many of them were low budget with poor production values - but others survived.... most notably Casablanca and Citizen Kane. Modern color film-noir (future noir) examples include Blade Runner and Dark City.
Maybe you can control lighting using visual coding tricks or day/night value setting in the XNL code.
Have you ever seen screenshots of the indie game Darwinia? The darwinia developers achieved something quite interesting by fusing 8bit sound fx with visual homages to old video games and the Disney film Tron.
Nice work.
Edit: Space sounds - Vangelis/synth music fits space themes, those funny old 1950's sounds that accompany Sputnik satellite black and white film stock animations (beep.. beep.. beep) and submarine sonar sounds .. ping ... ping... ping and even the goofy star trek 1960's computer sounds. very funny.
Note: No 4- Bush object? just checking since it didn't render on my map.