I have no advice, not having had such an experience (not at the level of graphic intensity you refer to). So what follows is all highly theoretical from my part.
If I were in a similar situation, I would try to take the events represented in the photos as facts, hoping that I could learn from those; if nothing else, I think it would be a terrific opportunity to prop up my own dedication to a practice promoting peace on earth — I would think something along the lines of "the very passions that caused these events to pass are still operating in me, in the form of greed, anger, indifference, etc — let these images feed my determination to put such passions to an end."
It's not a thing of the past, either — it still happens every day. Try "civilian war victims," or "starving child", on images.google.com, you'll find many modern-day photos. For some reason I find it so easy to forget that this happens every day!
There was a period during which I was recurrently assaulted by the image of a hunger-stricken war-torn african child (such as
this one). This motivated my practice quite powerfully at that time. I eventually fell into a severe case of over-striving (tension, fatigue, frustration), and stopped using that kind of fuel for practice.
But it occurred to me now that it makes sense to be as happy as humanly possible

I owe it to these people, not to weep for them, but instead to weep no more, else I remain an accomplice of the human tragedy

Perhaps such a frame-of-mind will help you see these images as facts, and have such an experience nurture your felicity, rather than your despair. If you choose to do so, of course.