I was reading yesterday a topic from 2006, about perlin noise clouds, and then i got interested in it; so i did some research and built this simple app to create a cloud texture from Perlin Noise. In case you dont know what is it, go here.
To know more about random cloud textures, there is also this interesting site, where they explain how their utility works, and where i learned about the technique.

I will be using this system in my 3D game, since random clouds are MUCH better to the eye than some random spray strokes or even a repetitive photo.

Cloudy Sky 1.4 Extension topic
Cloudy Sky 1.2 Program


This is a screenshot from my game, that uses the extension at runtime (together with the GmNomonic Extension for the skybox):



Program:
When it loads, it instantly asks for information to build your clouds.
It will ask for:
Perlin noise resolution - acts like a zoom option, smaller values give bigger clouds.
Cover level - Percentage of the sky to be covered in clouds.

Additional notes:
>GM7-made.
>Uses surfaces.
>This was not either difficult to make, or hard, it was actually fun. so no credit is required and you can use and distribute it freely.

[EDIT]
Update 1.1: Better interface and possibility for selecting texture size, and new options.
[/EDIT]

[EDIT2]
Update 1.2: extra checking, no previous errors, Extension added.
[/EDIT2]

[EDIT3]
Extension updated, version 1.4. Look in the extension's topic.
[/EDIT3]

Nice.

Update 1.2:

-Larger window, with a gray bar with some info
-Possibility to select texture size
-'Saving as'
-New, MUCH faster algorythm
-Options to regenerate texture or to reselect the parameters
-Fixed room_caption
-Fixed file version
-Fixed memory issues with repeated regeneration
-Runs in read-only locations correctly

Please comment, i want to know what you think about it.

I see you must be using a script to generate clouds(i got it to error XD)
Would you care to release it?
It sure would be useful for some games(like you said).

I plan on making an extension out of it, so that it is even more useful and easy to use.
This way it can be easily integrated in a game without resource conflicts and will be even easier to understand.
Basically, i turned the whole proccess in a 30-line script using 2 surfaces and a couple blend modes. With the new method, an extension can be considered, because it takes only half a second to generate a 512 texture. The old method (1.1) would take a minute to do that, because it used an adapted per-pixel mathematical algorythm which was, presumably, 100x faster on its original language ( C ).
The extension will probably have more options than the program.

Yes, But Only GM7 Users will be able to use it, With the actual script itself, You would be able to use it in all GM versions.(also, resource conflicts? What do you mean by that?)

if i use a script then all my variables must have crazy names so that they don't conflict with game resource names.
but, as my GmNomonic extension had this problem, i developed a system in which it uses a single array as memory, and it solves the problem.
I'm not sure if it would work in 6.1, or even 6.0, but... at the time of this post, the extension is complete, and it kinda works like the script. You install it, and it adds a function that does what the program do with 3, self-checking arguments, and returns a new background id with the alpha-ed texture. using this white texture, you can easily draw it blended and/or colored to create interesting cloud effects. also, you can have as much cloud textures as the computer can handle.
After dinner i will test it for bugs, and make 2 packs: the gm7 and (MAYBE) gm6 zips, with extension, script and demonstration usage.

If someone is going to use these packs, then at least add a link back to this topic in their game/program so that it is spread around the GMC.

Note: i don't like to convert stuff to gm6 because it is a long time since i last used it, and there are some obvious/unpredictable bugs in it; but, anyways, i will try to go try trying it.

EDIT

Update 1.3, extension added, extra checking to avoid errors, works with "treat new vars zero" off.
Top post updated...

just don't use health,global.lives,x,y or anything like that >_<
and keep the variables local, There are rareley resource conflicts, Let me see the script so i can make it GM6.1 Friendly(and not-resource conflicting XD)

This is an Extension.
I don't plan on converting it to previous GM versions.
And it would not even work on 6.0 or 5.3 because of used functions.
Thats why there is a program, so that GM 6 and 5 users can at least use pre-rendered images.
I like to protect my code.