Cornell’s institute for digital collections has archived and catalogued many different images of the demonic, monstrous, and marvelous things from antique books.
From the site:
“It will be useful, nevertheless, to note some general markers which have informed the choices implicit in these pages. In the context of western literature of the nineteenth and twentieth centuries, The Fantastic involves dread, fear and anxiety in the face of phenomena that escape rational explanation, or that reveal the notion of reality to be no more than a construct. A fantastic experience can therefore be likened to the breaking or shattering of a frame. While the literary fantastic is limited to the last 200 years, the Fantastic in art can be construed more broadly. This elasticity allowed us to choose images from works spanning a period from medieval manuscripts and printed incunabulae, to the early twentieth century.”
There are such gems as images from the Dictionnaire Infernal .