I'm pretty sure that this it wouldn't be legal to sell prints of this but maybe one of you guys know for sure.
If I use this photo from someone else:
and did this to it through a number of different effects in photoshop, and then vectorized it in illustrator:
does that constitute enough difference that I could say I was using the first image as a reference for my creation, and sell it as such without royalty or licensing fees? And also, let's say I made a screen print of it as well. So essentially being transferred to a different medium and in a different form.