No Rosie the Riveter per se, but the classic Norman Rockwell image of Rosie doesn't work that well for purposes of anti-bitterness icons. But these are pretty good. Originals are here and here.
I made two of the yellow ones because the first of them has a vaguely threatening feel to it -- don't be bitter, or I'll punch you! And the Anti-Bitter Army is not about threatening people who disagree with us; it's about making pre-emptive strikes against those we think may be bitter at some point in the future! Wait, no, that's not right. That kind of policy would be retarded, and not worthy of support. The War on Bitterness is about being positive in the face of negativity, and the second of the yellow ones gets that point across better. I kind of prefer the first one from an aesthetic point of view though.
But who says all icons have to be about bitterness? Here is a quick-and-dirty general purpose Rosie the Riveter icon for anyone who wants it. I stole it -- I didn't edit it or anything -- from the Rosie the Riveter Trust.
Now then, about Joe Louis. Joe Louis was, when WWII started, the heavyweight champion of the world. On his way to the title, Louis fought, and was knocked out by, German boxer Max Schmeling, a favorite of Adolph Hitler. Hitler frequently cited Schmeling and the first Schmeling-Louis bout as proof of Aryan superiority. In 1938, after Louis had won the title, he and Schmeling fought again, and this time Louis demolished him. The fight was over in less than three minutes. Louis became a national hero, and Schmeling's defeat was widely viewed as defeat for Hitler and Germany, much as was Jesse Owens's victories in the Berlin Olympics in 1936.
When the US declared war on Germany et al in 1941, Joe Louis enlisted in the Army. Recognizing his popularity and the symbolic value of his identity as the man who beat Hitler's favorite boxer, the Army launched a recruitment drive featuring Louis. He was portrayed on a poster in full combat gear, accompanied the the following text: "Pvt. Joe Louis says: 'We're going to do our part... and we'll win because we're on God's side.'" Despite the image on the poster, Louis never actually saw combat; he mostly staged exhibition fights to boost morale and to raise money for the Army Relief Fund.