Thanks for all the comments! Lets see what I can do to answer them.
Moodflow: Not sure exactly what you mean by the blurry clouds? Were you thinking that they should be somewhat noisier?
O_B: The foreground is not an image map, that was just my fault in the processing, somewhat overzealous with the dodging. I have uploaded a reprocessed version that is just a levels and curve adjustment for comparison.
FranK: Amazing eye catching the invert profile! I can't say I would be able to tell just by looking at an image. I know the invert is there but except for one cloud in the background it is not too noticeable to me.
Martin: I used a distance shader to render out a seperate distance file then used depth of Field Pro in photoshop to add the blur just to soften the close edges. I think it works nicely, but this version here doesn't have it for comparison.
I will add this and a second file coming soon to the cloud library.