[A-Pek]

try taking a photo background (any photo) then on a new layer applying your render/clouds (also try difference clouds for more contrast). use a large, soft(pressure-wise) brush for your erasor and delete some of the clouds. mess with the opacity or hue (anything like that) till it looks good. it'll give you a nice cloudy effect over a photo backdrop.

that same effect i'm talking about was used to make this sun flare (a LOT more steps went into this but you get the idea).
http://www.teamaftermath.com