I've now added the new check to the diagnostics for incomplete sequences of images. In addition to poems which have no images at all, there are also a few poems which are listed in the diagnostics output like this:

Poem #9095 Book VI (Blackwood's Edinburgh Magazine) (expected page count: 5; actual images: 4.)

This check can't really take account of the relatively small number of cases where page numbers are not pure numbers; for instance, if the page-range is specified as:

354a-354b

or

xx-iv

it's not practical to try to figure out how many pages should be in there.

I've normalized all instances of abbreviated pages so that e.g. 227-28 becomes 227-228. But again, I can't easily do that with non-numeric pages, so there may be examples like xx-iv where only a human could really deduce that it should be xx-xxiv.