I currently use a ZDoom format, but I don't work any scripting into the maps, so they should largely be vanilla playable.
DarkerDark, they aren't co - op at the moment, but I'll go back over the older levels and put it in. ^_^
Really, if you're using a ZDoom based format you might as well roll with scripting; the map format itself, as far as I know, is something that won't be compatible with the barbones vanilla game (Let's be honest, who here runs MSDOS or Windows 95 to play Doom? And yes, some people use Chocolate Doom, I know, but really. ZDoom can into features. Let us into features, too.)
I don't know of much scripting, but I'll look into it later. See what it can do. I rather like my vanilla doom, so I'd have to make it a separate project, but I do agree that the scripting can do good things (check out Tribute : This is not the best WAD in the world to see what I mean.)
I've fiddled around with the Doom map builder but never finished building a level.
If you'd like I could probably build a complete level for you, but I can't promise it'll be all that great.
Bouchart, if you want to, it would be nice to play something from other forum users. ^_^
My levels aren't particularly good either. I try to capture somewhat of a Doom 1 mixed with Doom 2 feel. I know a lot of mappers use custom textures and such, but I stick with the vanilla stuff, mainly to keep it classic.
But if you just want another map full of enemies to shoot and secrets to discover, I'm sure they'll prove adequate.