Tomahawk nose art by Bert ChristmanAllen "Bert" Christman of the AVG 2nd Squadron (aka the Panda Bears) had been a comic-strip artist in civilian life, most famous for his work on the "Scorchy Smith" series featuring an American mercenary pilot in South America. Then life imitated art, as it often does, and Christman became the pilot-adventurer he'd drawn for the comics.
I don't know how many of these sketches were applied to the AVG Tomahawks, though Terrill Clements says that the cowboy did make it onto the fuselage of the Tomahawk crashed by Tex Hill on the first night of the war. The cartoons are inside jokes: Jack Newkirk as the well-dressed party boy, Moose Moss with a jug of moonshine and a checkerboard, Gil Bright parachuting to safety (he was in a mid-air collision with John Armstrong on September 8), Tex Hill as a cowboy, Peter Wright as an uptight easterner. Apparently the drawings were done at Toungoo before the outbreak of war. (The spots that appear on some of these drawings might be panda footprints. The numbers are the fuselage numbers of each pilot's Tomahawk.)
These sketches were emailed to me by someone, whose covering message I've lost, so I don't know his name or where he got them. But here they are.