Luckily for you, you’re speaking to him.
I have the original file on an old laptop somewhere and could get at it if need be, but I think I remember what I did. I drew a green circle, gave it circular transparency (so that it gets more transparent the closer you are to the outer edge), then put a fractal cloud transparency over the top of that. Doing that with a couple of circles and overlapping them produces something like this:
I think something like that could work really well for the compound clouds in-game too. This is what the above looks like without the alpha noise, pretty similar to the compound clouds at the moment:
Don’t look at it too long. It might do weird things to your eyes.