This may be an unusual post... but cloud images can really come in handy when useing photoshop
here's a zip full of cloud pics I have taken and collected:
(93 pics) = (51.1Mb)
http://dl2.uploadgalaxy.com/files/07..._Pics.zip.html
here are some examples of how I've used them:
image1 image1edited image2 image2edited
I have also used them for steam and fog effects