Six onion-roof towers supporting heavens

[Koen G]

Which makes the absence of any definitely recognizable religious imagery even more remarkable.

I've long believed that too. Even in books about what we consider secular stuff, you'll have the odd Jesus here and there. But it is possible to have illustration cycles without religious scenes. In those cases, the texts makes it clear that everything still connects to Christian dogma and morality. See bestiaries, Ovide Moralisé... 

Now, the vast majority of the manuscript shows plants, astrology or text-only pages. So the room for folios where we can call the lack of religious imagery confusing is rather limited. Quire 13, basically. And who knows what that is about...