When it comes to tracing images, the only value I see in it is it saves time. And possibly that you get a more accurate picture of the subject. I don't feel it's okay to copy something unless the original artist gives their consent. Otherwise, it's not truly your work. And you must  give the original artist credit to copy something. If you copy something and pass it off as your own, that's when you get into trouble. You have to change it in many ways to call it yours. With our projects, we have gotten our inspiration from various sources, but we have changed the work to make it our own. We don't just post the original and say we did it. That's copyright infringement. we always change it.