At first I found it a mixture of creepy and intriguing, but after a while of being there (I was there for a LONG time taking pictures), I honestly found it more funny than creepy. Some guy was wondering what to do with all the bones... and decided fuck it, he was going to decorate the place with them. It's like macabre upcycling.
Some of the things were actually kind of whimsical, now that you mention it. The coat of arms, or crest comes to mind. I do have to wonder about what that person or people were like to talk to. As in, were they well-adjusted and cheerfully going about their work or something else?
The guy who did it was FrantiĊĦek Rint. Your guess is as good as mine as to why he did it though. I like to think that he was just doing it for shits and giggles rather than to create something dark and scary.
Man, this exchange makes me want to go back to Prague even more. It's a cool area and I'd really like to spend more than a week there, just getting to know the place. By any chance did you go to the natural history museum there? A bit homey for a museum if you ask me, though I did enjoy it for what it was. I remember that the model of the mastodon (or was it a mammoth?) was missing quite a lot of its hair.