Welp, I finished up some skies. Hopefully the day's worth of work was worth it :P. I zipped up the skies, the psd files, the scraps, and a test map, which you can grabify below:
Here are some previews (256 tall versions):
I redid the spacey sky first, which I think came out pretty good looking. There's not much changed from the previous version other than some new, non-repeating mountains and an update on the blue wispy stuff. In hindsight, after studying the D64 source material, I think the blue stuff in the sky is actually supposed to be some sort of outer space gas or something.
After that, I did three more skies - a brown sky/red mountain, blue sky/grey-green~ish mountain, and a red sky/brown mountain. This somewhat follows what's in Doom 64 up to the red/green fire skies in the latter half of the game.
These are about as close as I could imagine what the skies might look like if they were in Doom 2 (using my own methods and styles, obviously). A big obstacle to overcome is the palette, which can't really emulate the Doom 64 moody skies that well at all. The blues, for example, are super saturated and give an almost cartoonish vibe to things that use it. So I had to improvise for the purple~ish sky you see in maps like Terror Core, and just go full blue. The plus to this is that it gives off a Doom 2 style vibe, which I suppose is the entire point to this project. Also, I thought it might be appreciated if the clouds in each of the skies was different, unlike what you see in Doom 64 (where the same texture is used, but just colored differently).
I'm pretty sure improvements can be made to these skies. Mostly I was starting to get worn out working on them, but I tried to make them as clean as possible. The mountains in the red and blue cloudy skies really need cleaning up. In the instance of the blue sky, I tried to make the mountains somewhat darker than the others, but it ended up cutting out lots of the details.
I dunno though, I tend to be my own harshest critic. Let me know what you guys think :)