 Re: stock photos
Unfortunately, I think the right answer is yes you still do need the commercial license. Even though you might change it a bunch, or only use certain elements contained in the photograph, you are still using a photo taken by someone else. They did the work to take the photo and they get to control its use even if it will ultimately be unrecognizable as their original photograph.
Oh, and something else I learned here on the forum recently. Say the photo is of a celebrity, even the photographer does not have the right to sell the photo to someone who might market consumer products like t-shirts and such containing that photo. | 
