Yesterday I collected all the illustrations I could find (including some completely new ones, like 5-16-1 The Hog's Head), because the one good thing about the site's new version is that (in most cases) the quality is better than it was in the Moments.

I don't know if I just haven't managed to find them in the chaotic new website or if they're not there, but there are several illustrations still missing from my collection. I haven't checked books 5-7 yet, the number of Moments from books 1-4 of which I haven't found any illustrations yet is 16, 14, 12 & 10 (How weirdly consistant!).
And I swear I've seen it on the new Pottermore but hadn't collected it then: book 4 chapter 12 Moment 1 Moody/Crouch Jr. arrives at Hogwarts. That one eluded me. Maybe if we had an index or could search illustrations, I would be able to find it again!