I went searching for some free public domain images today to use for my review of Iliazd’s 1929 novel Rapture, and some of best engravings I found of the Caucasus were in a book called The Frosty Caucasus: An Account of a Walk Through Part of the Range and of an Ascent of Elbruz in the Summer of 1874. (Looks interesting!) It was scanned from the Bodleian Library collection at Oxford and can be read here.

Just a handful of illustrations (engraved from photographs—seems redundant.)