My own 2 cents, sure to rankle some sat-upons:
I think (adult) people should see pictures of things like this. It should be driven home just what the carnage is. The damage of not showing these things is that it becomes normalized, as is happening in the US just now. "Oh, another school shooting today? Change the channel and let's see what else is on."
In an age where news, politics and other current events have become entertainment people need to be reminded of what it really is. Pictures of dead bodies etc are not there to amuse, but to be sickening. It's like taking a bitter medicine. I think when people call for war they they should not think of the heroes doing victorious poses with their flag, but rather of the piles of rotting corpses, and realizing that could be themselves and their own children. Teddy Roosevelt had a noble perspective on war, "the measure of a man" etc but after losing all his sons in WWI his perspective on this was very much humbled.
I am not a pacifist nor against gun ownership (though I would prefer that my raving alcoholic wife-beating neighbor did not own one), but I think when people call for violent solutions they should be cognizant of what exactly they are supporting. With so many people cramming the media with "don't believe what you see, believe my words" these graphic images are necessary.