I avoid using anything labeled as commissioned or an oc, but I really wouldn't give a hoot if anyone did that with my art. Half the people who use references either don't follow it exactly or flit through images and characters faster than I go through my socks and have no attachment to the physical appearance. It's just something you put in the front of the rp. I don't feel I've lost anything until it gets in the way or my profits or reputation.