I come to you guys for wisdom and credibility. One thing I will do now on whenever selling or promoting is add a watermark. I hate them, but it protects your crops integrity, gives you credit for your photography, and hopefully stop these people from inappropriately using what isn't theirs. If I ever use someone's I will ask them and someone would like mines beyond Facebook "share" or here I would gladly send one without the mark.
I don't plan to be big-time, but I see a lot of questionable sales on some sites. Your input is always most welcome.