[Espy]

So uh, I personally dislike referencing art for anything, so I never trace. (Except the few times I was required to do that in art class.) But back when I was learning anatomy, I did try to eyeball it and copy some poses, positions, whatnot. I think that's fine. Any more than that, and I usually ask the original artist if it's okay to post said stuff. (I know that most artists are fine with people just /referencing/ their art for learning purposes.)

But I feel like asking first is always common courtesy, and if permission has not been given, then tracing (or even copying, really) can be considered theft.