Mushroom cloud

Ok guys, I'm just looking for any advice or tips you may have for me. I want to make the mushroom cloud in this scene more realistic looking but I'm not quite sure of the best way to go about it. Any ideas are appreciated.

http://0ut.home.comcast.net/help.jpg

Am I in the wrong place? Isn't this where the Photoshop experts hang out?

It is, but patience is also required ;)
I would suggest using the rubber clone brush and drawing in more of the cloud. It looks very empty, not realistic. Other than not messing up the skull, just 'clone around' until it looks right.

How patient am I supposed to be?

Yes, there are lots of people here who are good with photoshop.

No, they do not know everything.

Yes, it would be a good idea just to get a picture of a real mushroom cloud, edit the hue in Image > Adjustments > Hue/Saturation to fit the color scheme of your picture. You may want to use the magic wand tool or the eraser to get rid of the background on the picture you get of the mushroom cloud. Reducing the opacity or blurring it might help to.

That's basically what I did for this: http://www.swankstudios.com/dump/war.jpg

Well if you guys don't know everything...who does? That's the person I'm looking for. :D j/k

Thanks for the advice so far. We'll give it a try.