It wasn't until very recently that I realized that the picture was actually of manager Charlie Grimm. The original image comes from this 1941 wire photo:
GRIMM TAKES OVER AS MANAGER OF BREWERS
Milwaukee, Wis.: Charley Grimm, former manager of the Chicago Cubs, coaching back of first-base in night game between Minneapolis and Milwaukee Brewers, after he had taken over job as manager of the Brewers. The Brewers lost the game, 8-4, the first since William Veeck and Grimm joined the Brewers with several of the Cub players.
(collection of Paul Tenpenny)
The two uses of this image, wire photo and program cover, reflect Jolly Cholly's two periods at the helm of the Brewers.
His first managerial stint, started in 1941, lasted through the beginning of the 1944 season, when he was hired away by the Chicago Cubs. While Grimm was in Chicago, the Brewers were sold and resold, ending up in the hands of the Boston Braves in late 1946 (a move which spelled the end of the Brewers' long run as an independent ballclub).
Grimm was fired by the Cubbies in 1949, and the Braves hired Grimm to manage the top rung of their farm system ladder... the Milwaukee Brewers. To celebrate his return to Borchert Field, the Brewers dug out an old wire photo of the skipper from his previous stay in town, dressed him up in Owgust's beer barrel, and put him on the program cover.