“Get it all on record now - get the films - get the witnesses - because somewhere down the track of history some bastard will get up and say that this never happened.” - Dwight D. Eisenhower 1945
The image is a black and white photo of a large pile of human skulls and bones in front of a barbed-wire fence.
There is also https://en.m.wikipedia.org/wiki/Auschwitz_Album and https://en.m.wikipedia.org/wiki/Nazi_Concentration_Camps_(film)
The latter hits hard. Unbelievable images. Luckily not in color.
Can be watched at https://www.spiegel.de/geschichte/was-die-deutschen-nicht-sehen-wollten-a-9e63991b-cd26-4169-9fe8-bb118bf404e4 if that’s not geoblocked.