I have been reading the books loud for my eldest daughter for the last year or so (I have ½ hr reading session with both my kids almost every evening), and I read the Danish translation, so I have no idea what the various creatures are called in English - but the riding animals used by the Knights of the Academy and the Free Plains Lancers are very squig-like in appearance (just with 4 legs).
The academics of Sanctaphrax could be represented by all kinds of cultist models, just painted with the right colours/checks.
But the main problem would be, that many of the visual concepts are just too Unique to be proxied.