Maybe someday when I'm better at making doom wads I'll host one and as project lead.
spoiler
btw I'm bagsying the map name "A Spectre Hangs Over Europa" in case we ever do make one
Edit: just to be clear this is just me seeing how many people are interested, I don't feel I have the experience to run a community project at the moment and am currently working on a solo megawad on the side anyway. However, if enough people are interested I'd like to make it some day
Doom textures have a height limit of 128 pixels I think but can be quite a bit longer horizontally though the widest you'll see practically is 1024 pixels wide. The interesting thing is that floor textures called "flats" can only be used on floors and ceilings (and normal textures can only be used on walls) and have to be 64x64 pixels large (no bigger no smaller).
Really though this post was more to test the water to see how many classic doom mappers there were that were active on hexbear than anything - I don't feel like I have the skill or experience to lead a community project right now.
I have no classic doom mod experience. I've done The Sims (the first one), TF2, HL2, San Andreas (which is a huge pain because of the naming conventions and file structure). Now I just make stuff for Unreal because it's so easy and widely used. It's all kind of the same idea though.