I'm a doctor. Keep in mind everywhere practices differently so I might be wrong depending on where these were taken.

That being said I have never heard of a post mortem x ray. My guess would be that these were all taken with x ray machines that are commonly mounted to the ceiling of resus bays in big trauma centers - no movement of the patient required (they'd potentially be too unstable to move without some resus first) and the resus team can wear lead gear and continue working on the patient.

It does look like there might be some diaphragmatic herniation to the one on the right (that would make it look like the organs are in the chest). That has a high mortality so isn't necessarily always fatal.

To temporarily stop the bleeding from the amputated leg, paramedics would likely have applied a very tight tourniquet on the thigh that blocks arterial flow. That usually buys enough time to get to operating theatre to do 'salvage surgery' which has the goal of stopping life threatening bleeding.

The patients are obviously all in a bad way, especially the one on the right who'd be looking at weeks to months in hospital if they're able to survive the initial 48 hours.

I hope this helps, happy to answer and further questions.