The necessity of posting a photo of an accident is certainly open to personal opinion. Of course, a person holding a photo can (and often should) choose to keep it to themselves. And, a person may post a photo which is inoffensive, and widely appreciated. In between those situations, a photo may be questionable. I don't think there's a hard line of may/may not be posted here. In my past role of 27 years as a volunteer firefighter, and photographer, I took a lot of photos of sad events. a few of them found their way into the public domain with the Chief's okay. My (and the Fire Department's) criteria were: The photo may not identify a person who was a victim in the event. The photo may not show an injured person (identified or not), nor direct evidence of the injury (any amount of blood or worse), and may not be the first to identify a vehicle (license plate numbers, but extends to aircraft registrations too). If the vehicle has already been publicly identified, less of a concern, though I never allowed a license plate number to appear in a photo which went public.
Photos of damaged vehicles, sad as they are, may allow people to better understand the circumstances, damage to the vehicle, and perhaps configuration of the aircraft when it crashed. Such photos should also prompt viewers to consider what they might do to mitigate injury where they to be involved in a sad event. Every photo of a plane crash with cockpit damage should prompt us to think about seatbelt use, egress, and perhaps wearing a helmet in certain types. Crashes into the water should remind us to wear a life jacket (one saved my life). And, photos, when offered with a description of what the pilot was doing, might remind us that we could choose away from that maneuver ourselves.
So, PPRuNe expects good judgement and simple empathy in selecting photos for posting, but some accident photos are okay to post. FWIW, I recently deleted photos posted of the cockpit of the recent 737 crash in India, Though they did depict control settings, they also obviously showed direct evidence of personal injury, so no.
On the topic, of "serious", "life altering" injuries, we are of course empathetic to other people and our fellow fliers. I can say that considered with a positive mind, "serious injuries" can be overcome, and lots of things alter our lives, so it's up to us to find the best possible path to get on with it. I met many people in hospital who obviously would have a different life going forward, and they still were positive and looking forward in life. I has reminded me to take nothing for granted! Your health and fitness is not guaranteed! Appreciate it, and maintain it as best you can! Photos may remind us of this reality....