FRONT ROW - San Diego, Oakland, Detroit, Seattle, Arizona, Cincinnati, Baltimore

MIDDLE ROW - Cleveland, Tampa Bay, Toronto, St. Louis, Miami, Minnesota, Texas, NY Mets, Chi Cubs, San Francisco

BACK ROW - Milwaukee, Philadelphia, Colorado, Boston, Kansas City, Washington, Chi White Sox, Houston, Pittsburgh

NOT PICTURED - Homer (baseball-headed guy from Atlanta), and the three teams that don't have mascots (NY Yankees, LA Dodgers, LA Angels)

Source: http://reddit.com/r/baseball/comments/2ariww/its_officially_a_party/