In the Ormsby Psalter (which is in the Bodleian, and digitized online), folio 109r has a snail battle directly opposite a rather snail-shaped letter Q.
(The illustration program seems to be: a grapevine, marking Psalm 79/80; a battle of a goatman with sword and shield vs. a lion/unicorn woman, with a pot and spoon; a dog with a hood looking backward, and a startled pig face on his butt, also looking backward (and thus pointing out the location of the psalm commentary about “Lord, turn us around, and show us Your face, and we shall be saved”).
(Then there’s a musical party scene in the letter E, illustrating Psalm 80/81, “Take up a psalm and give it the tympanum (playing bells with a hammer in the picture)… with the harp… blow the trumpet….” There is the Q in “Quia preceptum,” and then, on the other margin, there’s a snail. A human man is dropping sword and shield and running from the snail, which seems to go along with “Iudicium Deo Iacob.”)
(At the bottom, “his back” is right above a picture of two half-naked men wrestling, thus showing their backs, along with a donkey-man referee with a naked butt and legs at “burdens.” Presumably because donkeys carry burdens.The word “Divertit” is right next to a picture of some kind of bird, of the kind named tits; and it has its neck at a weird upside down angle to represent divertit’s meaning, “to turn away.”)
So yeah, it’s more entertaining than chapter headings, and might have helped with memorization of the book’s layout or contents.
I don’t know what’s up with the acorns, and the dragon vs. leopard dragon thing.