This has happened to me quite a bit, at first I asked people to take them down, at this point I don't even care anymore x3

Way I see it, I'm the only one verified with my pics, anyone else who uses them is just spreading my name for free

I'm sorry to hear that. I too have had a similar case with someone on facebook who says they got a pic from my gallery via search engines. I told them that it was no excuse to use a pic of my char for their facebook page. Since then I made a poster to warn and hopefully deter people from taking ones art and claiming it for themselves. Here: http://www.furaffinity.net/view/14121182/ . I've pointed it out to everyone who watches me that all the stuff in my gallery is copyrighted to myself and whoever I commission.

Well, yes. There's only so much you can do. There's a "so bad it's good" sparkles and glitter photoshop floating around, but the site has no way to report it. I figured it could stay since it was so amusingly bad. XD

For f-list, it feels a little more personal since most art is of my OC. It feels just a little disturbing to see someone appropriate that identity (more so than the art).

That is terrible! I've only recently had a similar situation where someone used a commissioned pic of mine for their facebook page! I think this might be a handy little item to add to your gallery: http://www.furaffinity.net/view/14121182/. Feel free to use it if you want to. And in my opinion I would put my foot down and take action against these thieves. At the end of the day it's your creativity and you should be credited for it.

Sorry it's http://www.furaffinity.net/view/14121182/ without the full stop.

Ah thanks. Yeah, if I spot them, I'll report them, but sadly it's not easy when people just snatch them from Google Image Search.

Ah well, if I see them, I'll report them. That's about the best I can do.

It's the best thing to do. The only other thing I can suggest is possibly have some sort of copyright watermark in your work.