I think our brains are pretty good at ignoring or abstracting/simplifying things we see that we don't understand, almost too good. That's just magic, optical illusion, or hallucination. Getting high is like chemical circuit bending. I feel staring into the void alone won't be enough drive one mad, it's when the void stares back and forces awareness, or knowing, that one has to worry. The non-euclidian architecture of R'leyh is just unsettling, but the stare of a multidimensional being can't help but bend your circuits beyond their limits.

There was that one short story though about FTL travel, wherein the conscious passengers must be asleep for the journey through hyperspace (or whatever that story called it). Some people stated awake through the trip and came out the other side mad. The hyperspace itself wasn't enough to break their brains though, it was just that an instantaneous trip from the sleepers' perspective, became an infinitely long (in time) trip from the waking conscious perspective. At that point, what they saw didn't really matter, it was a forced perception or awareness without the solice of "not knowing" that broke their brains.

None of this is science, just rambling nonsense.

It would just look stretched and/or rotated.

Basically, you can see the back side of the object, because the object moves out of the way of its own light.