Single Status Update
Publishing some ideas I had. I hardly map anymore so you guys probably need them more than I do.
1. The player is seemingly stuck in an endless loop of teleporters. He needs to find a shootable switch that is barely visible from one of the portals and activate it in order to advance.
2. The yellow door isn't marked with the usual DOORYEL. In fact, it doesn't even have a door texture and looks like a regular wall. Instead, there are a few series of DOORYEL marks (like in Plutonia Map11) that all lead to the same spot. The player must conclude that the door is somewhere in there and try pressing everything in that room.
3. There is a shootable switch the player has to activate but only SSG can shoot high enough. Now where is that bloody weapon... (alternative speedrun route: bring the arch-vile there)
4. The player tries pressing a repeatable switch and it seems like it's useless. But actually every time you press it the nearby door opens by just a few units. (maybe tricky in complevel 2, easier with a rising bridge for example)
5. New object: indestructable movable barrels with very low mass. The player has to construct a bridge of sorts and then barrelrun on it to the exit.
6. Map15 of a megawad: the exit room has thousands of switches, exit pads, etc. One of them is the secret exit. The player has to look for clues around the level to figure out which is the secret one. Or he can just bruteforce, but that might literally take hours.
7. A map that is broken somehow (e.g. a blue door actually requires yellow key) so it is seemingly impossible, but there is a speedrunning trick you can use to reach the exit despite that.
8. Lead a caco or a harmless PE somewhere you can't reach to activate a lift.
9. At first the lava area seems impossible to cross but actually you can use the Alteus trick to avoid taking damage (stand on the edge of the sector so the game thinks you're not technically touching lava).
10. Map07 of a megawad: At the start the player can choose between "I want a boring Map07 remake!" and "Give me something completely different". Satisfies everyone.
11. A huge horde of monsters and rows of invisibility spheres everywhere. If you pick one up you're probably dead because you won't be able to dodge everything. So you have to maneuver between them.
I also had some concrete wad ideas.
Knee Deep in the Dead: The Hot Springs Special - in this special episode of KDitD that was released only on DVD due to unairable content, the doomguy takes a break and goes to a hot spring. In the onsen area there are holes you can use to peek at the imps on the other side. I thought of this because the E1 sky really looks like something you could see at a Japanese mountain hot spring.
Toilet Break 2: The Taco Bell Incident - dunno what the map would be like, but the name sounds kickass already.
A Michael Jackson tribute with all maps having midis of his songs. Or any other artist you really like.
A map like all these "room escape" flash games. No monsters, you just have to inspect a few rooms carefully, look for clues, etc. Could be interesting I think.