I dreamt that somebody came up with a symbol that would cause you to die if you looked at it. I’m not sure exactly what the symbol was, but it was an 8 by 8 grid of single-digit numbers and a few lines. (Matrix mathematicians beware!)
The funny thing is this: Nobody believed it when told. They’d demand to see it, snatch it out of the person’s hands, and as they are collapsing to the ground loudly declare, “See, I told you so.”... their final words.
And this would happen over and over again. One person watches someone kick the bucket right in front of them, refuses to believe it, grabs the symbol out of the dead person’s hand, and again proudly announces in their last two seconds of life that they knew it wasn’t true.
Here's a serious science fiction story dealing with that basic premise. (And of course there was a Star Trek: The Next Generation episode where our heros propose destroying the Borg this way.)
I'd note that while it's impossible (literally and with mathematical backing) to rule out the existence of an image that could "crash" the human mind, it would likely be very different for every person, not the same for everybody. And failure-to-process need not manifest as "crash"... I think optical illusions are basically exactly such a failure to be able to express an image using the biases of the human mind, and the power of an optical illusion tends to top out at "giving me a headache". Although, to be fair, they do sometimes do that, which is pretty impressive for a simple image.