Cassius Coolidge illustrated at least two books, The Independence Day Horror at Killsbury and Prophet of Peace. Both were written by his first cousin Asenath Coolidge. They were published in 1905 and 1907, respectively. Therefore, they are in the public domain, and am I allowed to post the illustrations from them. (If this is not the case, please let me know.)
I am not much of a bookworm so I have not actually read either book, but just looked at the pictures. There are not any dogs playing poker, but the illustrations are still well done and interesting.