The picture I linked is of a buckwheat pillow. Had no idea they were a thing before today.
What about silk or bamboo pillow cases?
I’ve only ever really used cotton pillow cases and cotton stuffed pillows. I recently upgraded to a foam pillow that I’m enjoying.
The issue with either is from the risk of popping/leaking: if your pillow leaks, your entire mattress might be fucked. The risk vastly outweighs the improvement