Wow, fucking bone chandelier!
I remember the story from Kudowa-Zdrój Skull Chapel that it was meant to be a warning about tragedies of war since war casualties' bones were used there.
I can imagine only one more reason to build such thing - to warn your enemies :D Well, waiting for your post.
I don´t know the story behind the Kutna Hora Ossuary but now I got curious about it and will do my deep research to find out :D ;)