Did you try fluids->getFluidExample->afternoonClouds ?
You could try modifying the texture settings on the fluid "cloudLayerShape" in this file. Lowering the ratio will make the clouds more rounded. It is using a perlin noise with inflection to make the clouds pluffy looking. If you need more rounded shapes you could try using the billow noise and turning off inflection, although keep in mind that billow takes MUCH longer to render. The billow noise is the sum of a bunch of randomly positioned spheres.
Duncan