Here's the ruling on that (according to Wikipedia, can't find anything about it in the official rule book on mlb.com)... "No images of baseballs: No "pattern that imitates or suggests the shape of a baseball" may be used on uniforms. Notably, in apparent violation of this rule, the Toronto Blue Jays, Milwaukee Brewers, Los Angeles Angels of Anaheim, Florida Marlins and Philadelphia Phillies for many years had logos that incorporated the image of a baseball. However, while the Philadelphia cap logo clearly depicted the baseball, the logo worn on the uniform jersey did not feature the image of the stylized stitching indicating the image of a baseball. The Marlins logo, while depicting a baseball, can not easily be mistaken for one, as the team's namesake fish is displayed in front of the ball design. The Toronto Blue Jays had a similar design with a Blue Jay head on the front of the ball, and this logo was even used on the center (and later left-center) of the uniform itself. The classic Brewers "ball and glove" logo (with the team's initials, MB, stylized into the shape of a blue baseball glove surrounding a ball) made a comeback in 2006 on the hats of the Brewers' Sunday home uniforms and is now the Brewers' Friday home uniform. Also, many teams such as the Giants, Nationals, Rangers and the Mariners use uniform logos that clearly depict a baseball, the New York Mets have featured uniforms with a sleeve logo that imitates the appearance of a baseball since the team's inception in 1962, so it may be that the rule is not enforced, at least for caps. (The purpose of this rule is to prevent one team from deceiving the other. The National Football League has a similar rule, which states that no pattern that imitates or suggests the shape of a football)."