Base Ganymede : Complete by Khorus has just been released and it's a blast! The 3 episode vanilla megawad for Doom 1 contains a total of 27 maps, set on one of Jupiter's moons called Ganymede. Each episode has it's own progression rather than the usual one, so you can actually expect a lot of different settings. The mappack itself feels and plays very classic, so if you are into that kind of projects you will definitely love it. You can download the full wad from the /idgames archives. Enjoy!