OH, so it's using a greyscaled pallete.lmp?
If you like this theme you can also play original maps using Qrack and gl_greyscale 1.
Now this would only grey the map not the items/particles/entities...
hmmm well actually you should be able to use -game jam8 and play old maps with any engine in that case...using their modified pallete.lmp.
need to play these new maps either way!
would be cool to make a shader that would toss out some static or film grain effects.