I do remember (unfortunatelly I can't recall its name) a q3 map generated randomly, made by countless square blocks of different sizes. It was floading on a light blue sky background, IIRC. The author however specified he had to manually add some stuff to actually make it playable.
It was cool enoguh, but hard for performances due to its very high number of polygons, which were almost always drawn, basically being a "floating" map.
Found it: Lun3DM5 - You'll Shoot Your Eye Out
http://lunaran.com/page.php?id=218A modern PC can handle it perfectly, however take a look to it doing "/devmap lun3dm5" and then "/r_showtris 1"!!!
PS: @Sago or @Fromhell: do you think it may be possible to make "r_bloom" do not apply to r_showtris wirefames? Each time I want to try r_showtris, I have to disable bloom because of it being too bright!
PPS: reading that map description, it looks like that however the human decided the map design, although the "blocky work" was made procedurally...