I use the perlin noise but you can use Simplex or whatever too. Perlin is just most like the natural shapes in nature.:
You can do this for Free. It will cost you nothing.
Great looking package but no very suitable for phone use, you have almost 7 megs worth of perlin noise files, I am just rendering them in real time.
If you like my effect send me a PM, and I will hook you up. i have a bunch of other effects I will add too if you want them.
My effect uses no textures.The effect pack listed above in the store takes almost 7 megs worth of texture. My effect takes 2 8x8 sprite. and the entire file is 172k, less than one of the textures in the store version.
I can make some more effects too on demand, I made myself a template that is easy to change into other effects.