|British illustrator Cecil Aldin (1870 - 1935)|
with one of his furry subjects
Yes, you're free to sell the animal illustrations of Cecil Aldin. Except for his imagery for "His Apologies" (Rudyard Kipling's 17-page poem about a Scottish Terrier puppy), all of the artwork by Aldin (sometimes mistakenly spelled "Alden") is public domain. The works were either published before 1924 or were not timely renewed (according to the Stanford Renewals database). "His Apologies" was renewed in 1959, and the drawings are under copyright until 2027.