I have a few unusual requests here.
#1: New textures. We could dreadfully use some new textures for designing stuff. Sure, we have a lot of versatility when it comes to nature themes, or factory themes, but what about things like cities? Besides the Dark City textures, which are pretty much useless and ugly.
#2: New Ambiances. We have a bunch of waterfall ones, and lava ones, and some pretty much useless Disco ones, but that's not much variety. In my opinion, things such as ambiances can be a beautiful touch to levels. Some suggestions I have are sounds like:
-Birdsong
-Bubbling
-Machinery Sounds
-More Machinery Sounds
-Even More Machinery Sounds
-Buzz (Such as the one that would come from a freezer, or pop machine)
-Rustling Foliage
-Wind
-Waves
-Alarm Bell
-Alien Noises
-Laser
-Creaking Wood
-Insect Noises
Of course there are many other possibilities, but these just came to me off the top of my head.
Hmm, I had some more ideas, but I can't remember them anymore. Maybe later.
EDIT: Remembered one.
It came to my attention that Linedef 52, the continuously falling FOF, is horrible to use multiple times in one sector. For example, if I wanted to have a chute, from which multiple kinds of boxes would fall periodically, I'd have to set up an elaborate mechanism of different floor and ceiling heights. The reason for this is because the platform always starts from it's top, so if I give them all the same path, they'd be clumped together. I think the way this should be fixed is to make it work more like Linedef 60. Basically, 3 sectors, one that determines the topmost height, one that determines the bottommost point, and the main Control sector to determine the starting point.