Cats singing. Lithograph, 1817, after a design attributed to Pieter Bruegel (1525-1569). This file comes from Wellcome Images, a website operated by Wellcome Trust, a global charitable foundation based in the United Kingdom.
6 paintings of cats by Louis Wain (1860-1939) with an increasing degree of abstraction, attributed by some to his suffering from schizophrenia
Public domain, via Wikimedia Commons.

My Wife’s Lovers, Carl Kahler (1855-1906)
Public domain, via Wikimedia Commons