Artist Jeff Russell has an entire gallery filled with Lovecraftian tome illustrations. The creatures have a wonderfully Giger-esque feel. Purists will be disappointed that the depictions don't always hew to the Mythos canon, but they certainly capture an appropriately other-worldy aesthetic. That's complimented by the heavily stylized glyphs
I wish these were available as line artwork. They'd make awesome pages for a prop tome.