At the ZDoom forums, jimmy has recently released his fourth version of his mapset Realms of zoOn which is definitely a very unique experience when it comes to mods. Acually he doesn't tell you much but "Welcome to the world of the sleeping. The endless void of the uncertain subconscious. Can you defeat us" but that's already making me very curious if the screenshots aren't enough yet. Check the release thread and give it a try.