Well, if you work with a mapeditor for Doom, you will sooner or later come to a point, when you finish your first room in which you have at last 3 corners ;) The funny thing about this is, that it happens very seldom, that you add something in your corners. Your main focus always os set to the large plain walls, not to the corners itself, which connect these walls. That's the moment, when high quality and heavy detail starts. Normally I also don't add anything to my corners (sometimes some ammo, blood and bones, candles but nut much more) but in a few cases, the room cries something like: "Edit my corners, I look ugly!!!" and well, here we go ;)
Shot number 1 shows us a massive SUPPORT2 lightsource build directly into the corner itself. The mainthing you do, when you detail your one corners is the addition of some more corners, make 11 corners out of just 1 as the example shows us, and to be honest, without any arrogance: This looks just great :)
But you don't have to add always such a complex object to a simple corner. Sometimes it's just enough, if you add 2 more vertices and place some - so called - bordertextures to your corner (like SUPPORT, LIGHT, DOORSTOP, METAL and even DOORTRAK). It's a small change but the overall-result makes up for much more eye-candy.
Summary: Don't leave your corners as they are, add bordertextures or even add new corners and complex objects to spice your rooms up! It's worth!!!
Extra-Buildtime: "1-4 minutes" (bordertextures don't even take 1 minute at all)