Hi, OP here!
Wow thanks so much for your feedback on this topic!
I think the best thing to do would be to 'unsubscribe from images'.
That way you still get the updates, but dont have to see any pictures.
I didn't know you can do this!!! Thanks very much!
It would come across as a little SS to put up a status telling people what to do. If you don't like what they post, don't look at it.
Yeah, I thought it might. The only trouble is that the image is already in my brain in order for me to know not to look there

I am particularly susceptible to gory images, and one glance is, unfortunately, enough to get it stuck in my mind while I tremble and shiver for the rest of the day
I think there are two problems with the request
1) people will rationalize - "this isn't really that gory"
2) people will decide the message/cause is so important that the picture is needed for impact.
Either way they will probably decide your request exempts their post.
This is a very good point. My cousin-in-law (a medical student) likes posting images of diseased parts. I didn't mind is so much until she posted
one of worms crawling out of a woman's breast (and the woman was still very much alive). I couldn't sleep for 3 days after seeing that picture. Even though I only saw it for a split second, I just couldn't erase it from my mind. She says it's part of the human body and isn't gory at all - it is a fact of life! I had to hide her feeds permanently (and I missed out on her wedding announcement

)
Oh, not those pictures again! It's a virus and the person posting them does not know they are being posted. (At least that is how they were about 3 months ago and times before that. http://www.washingtonpost.com/business/technology/facebook-confirms-investigation-of-graphic-images/2011/11/15/gIQAHnalON_story.html )
I would message one person and just ask if they meant to post the picture. If they say no.. then I would also message the other person/people. Point them toward that link above so they know why it happened.
One more thing I'll add to this is that some of these gory pictures are fake--and actually, a lot of them are viruses. They may not be intending to post the pictures at all, but clicked on someone else's post of the pictures and got hacked. One example was that a lot of people were infected by a fake Osama bin Laden death pic last year (the death was real; this particular pic was not).
ETA: Yeah, what Squeakers said. That'll teach me to start a reply, forget about it for ten minutes, and then post it anyway. 

There are such viruses??? Oh wow, that is nasty. Thanks for letting me know! I was wondering why my sweet old aunt, who is almost 70, was posting something so disgusting

I didn't even know how to broach the subject with her.
Thanks again. I guess I will use my own discretion.
So the solution:If it's a medical student who likes posting specimens of her study, I'll hide the feeds. But if it's someone who doesn't normally post such stuff, I'll send them a PM to ask if it was a virus using these words:
'Hey, did you mean to post this really gory image? I know there's a virus going around, so wanted to give you the heads up this is on your wall!'
And if it's someone who appears to like gory stuff, I will defriend without explanation (I really don't know how to tell someone I'm defriending them because I think their posts are disgusting. Btw, I'm glad I'm not the only person who thinks this way:
Honestly, I would defriend someone who posted pictures like that on Facebook. And I think what they're doing is offensive enough that I'd drop them a PM to tell them why. In as neutral a word choice as I can.
What would you suggest as a neutral sentence? Could I write "Dear Angie, I am removing you from my friend list because I found your recent postings offensive"?
Is my solution within the bounds of etiquette?