1x1 is an MBF21 community project inspired by LunchLunch's 10x10 Project, in which he limited himself to using a set of exactly 10 textures and 10 flats per map. 1x1 originally started partially as a joke, after El Inferno showed off a ridiculously detailed and good-looking landscape that he had made using just a STARTAN texture and lighting + height variations. It became more than a silly joke though, and grew into a fully-fledged community project that was put together over the course of the last few months, where each mapper was restricted to using exactly one texture and one flat of their choosing, plus one switch texture of their choice and F_SKY (choice texture must be used as a sky transfer). Preview shots below, and you can find more in the linked thread. :)
Don't think I ever re-posted that inspirational screenshot that El Inferno posted, but I went digging for it a few days ago:
He also ended up releasing this map here as part of an exhibition of "unfinished maps" for PUSS XXIX: Hot Soapy Water, so if you're curious like me then you can totally poke around in it in UDB or whatever your editor of choice is, put down a player start and iclip around. It's fascinating.