These look weird because they are repeatedly and actively playing with exactly the early medieval images Tolkien was playing with. A few are more modern storybook, but at least one is FANTASTIC riff on the Bayeux tapestry. Another two are lifted directly from early medieval paleography (handwriting) right out of a textbook on Insular incipits (how an opening phrase or title of a manuscript was written). Another im pretty sure borrows from the Book of Kells; that’s definitely a specific image, I know that image. And Tolkien knew it too.
The figures look like, say, the illustrations in Old English Genesis A. There might be a little Eastern Orthodox icon style creeping in, or it might just be that that style has a lot in common with early medieval British and Irish manuscript illustration (ca. 600-1100 AD). These are great, and an extremely clever nod to the texts Tolkien was drawing from, and even the literal manuscripts in which he was imagining his work (or at minimum Bilbo’s work, in-universe) to be written:
As Tolkien says, “Further information will also be found in the selection from the Red Book of Westmarch that has already been published, under the title of The Hobbit.” (The Fellowship of the Ring, “Prologue: Concerning Hobbits”). Or, perhaps, in the Red Book of Hergest (Welsh, Llyfr Coch Hergest) — another Red Book of the West (or Wales, that is). Obviously The Hobbit does not actually show up in one of the most important medieval Welsh manuscripts (currently housed at Oxford), but from the very first page of lotr, Tolkien was playing with an incredibly specific manuscript history!
And this guy, Sergei Iukhimov, apparently clocked that shit on day one. And got a lil weird with it. Respect.