Just read through the "Royalty free art assets" thread, and have a related but different question of my own. So to note up front, I'm speaking specifically about my prototype - I haven't decided whether I'm going to self publish (probably not) or try to get my game published, but in either case, I don't anticipate this being my finalized art.
What I have been planning on doing is finding images that are either in the public domain (which is less of the concern) or in the Creative Commons with allowance for commercial usage AND allowance for modification, modifying the images a fair amount (to fit my style), setting up a Flickr account to share the Creative Commons modified images when required by the CC license, and using the modified images in my prototype. Note that in about 99% of my prototype art I'm using photographs that I'm modifying in GIMP, so there is a lot of CC source material out there and available. I figure, since it's prototype art, it's OK that I'd have to make some of the images publicly available.
Does anybody see any potential issues in doing this? My thought is, as long as I keep a page in my rules specifically listing credit for any CC images (original title and artist/photographer/username), and share the finished images in kind when required, I should be in the clear, right? Any thoughts are appreciated.