I don't think "the talk" helps kids or just seeing pictures of wrecked cars. I don't have any scientific data to confirm that though.
We had an assembly at the county fairgrounds about a month before prom. All the county schools piled into the grandstands. There was a "wreckage" under some tarps. Someone started talking over the loudspeaker giving a back story, then there were sounds of a wreck and someone pulled the tarps off the cars. Then there were area students in the cars. The kids that "lived" acted out hysterics and there was a 911 call over the loud speaker. Fire and rescue came and extricated some of the kids, some got blankets put over them and the coroner vehicle came in. I was an injured person and got a ride on the medevac, but I died in route to the hospital. They had some parents come in and cry in front of the wreckage. While fire/rescue was doing their thing, a pre-recorded message from the dead kids played. About how they won't be going to prom, graduating, going to college, getting married, and how sorry they were for putting their parents through all of that, etc. Some of the kids in the stands cried and it shook them up a bit, but I don't know that it stopped anyone from drinking on prom night.
A few of those kids were involved in drinking and driving accidents after high school. One became an invalid and died several years later, one died at the scene of his accident.
I'm not even sure if showing them mangled bodies would stop them, but I think it would have a bigger impact on them.