John La Farge (1835–1910, lived in Providence, Rhode Island). Bed-ridden early in his career and in need of the cash, La Farge produced fairly loose watercolour designs which were engraved by Henry Marsh (American, 1826–1912) and published as story illustrations in the Riverside Magazine for Young People. He later regained his health and turned to the more respectable, and probably more profitable, trade of stained-glass windows.
Lovecraft knew of him, since he mentions him by name in a letter to Moe, 24th November 1923. Lovecraft had written “The Rats in the Walls” a few months earlier, August–September 1923. An interesting co-incidence, given the picture seen above, I’d suggest. There was apparently also a ‘Bishop Hatto’ story by Sabine Baring-Gould.