Thanks for interesting.
I'm sorry if I'm misunderstanding your English.
So you don't like the sky texture of now version a bit, do you?
Yes, to be honest I myself think that it must have been better.
"Replacing ceiling texture" itself is very easy.
But it matters whether we are satisfied with a new result.
Gloom engine loads a ceiling texture from 128px*128px iff file.
Here is the sky texture in 1995 maze.
It gives 2 issues:
1. It is very difficult to express "clouds".
And we should pay careful attention to edge,
otherwise a strange (silly) issue would occur as following:
2. At this time Gloom Deluxe engine cannot show various "light blue" color.
To solve this issue, perhaps we should edit misc/palette,remap files.
Unfortunately now we don't know how to do.