Definitely some jewels in that presentation! There is only one that I know I've seen (but didn't know the artist). I'll bet that you would know which one.
I came across Khnopff first many years ago in a great coffee table art book on Post-Impressionism. His paintings always struck me as unsettling in an almost surreal manner. I quite love this portrait :
The eyes remind me of the old portrait photos – the ones that took minutes to expose – the eyes look pale and blurry because the subject's eyelids blinked and were caught on the film. (Or tintype or whatever.)