Uhh, I was sure slaughtenstein has only one exit. I checked for all linedefs triggering exit and 20% damaging sector. For some reason I forgot Romero head... whoops.
So as it is now, there is one tiny room with crushers leading to secret exit that serves no purpose. It could be altered to be mandatory to visit with exit revealing switch, so that room wouldn't be purposeless.
Also, map 25 has some black textures in opengl right in front of starting position. Same black textures like that are on lifts with cybers in map 15.
map07: contains modified iwad content (erm, the entirety of 'dead simple'), isn't that a big no no?
Not much to do about that by now, I suppose.
maps 04, 07, 19, 23, 28: no music? (I know for your maps it was intentional)
Also 31 and 32. With gggmork's midi surplus, I wonder why he didn't insert any to his wad. 32 would benefit from some spooky midi as well (silent hill is horroresque, right?)
On an unrelated note, I found this few pages back.
Island of Mystery - Map plays entirely fine, but while tinkering with it a bit, I noticed that there is a very obvious fastest and downright uninteresting uvmax route which would make maxing this map a huge luckbased bore. Simply pick all guns at start, make cybs infight and run off to revs/archviles part - when you're done with it and get back, infight should be over and how much stuff died off depends on luck. There really should be something done about this. I'd put stationary baron between blocky lines somewhere close to the entrance outside (far enough to not infight with cybs easily, close enough to make trying to take him out head-on suicidal). I hope this makes some sense.
I'm never sure if something I brought up is eventually forgotten about or disregarded as something unwanted to implement... so I end up repeating myself to an eternity, hah.