There is an interesting old article about King Novelty/Valmor Products on the blog PlanetBarbarella.

Valmor aggressively promoted the idea of romantic love with its products – not only would its skin brighteners and creams help deliver the man of your dreams, but perhaps marriage and a better life. According to author Juliann Sivulka, the advertising concept helped Valmor “successfully re-package Anglo-Saxon 19th century ideals and gender roles.” New mass media wasn’t just influencing white Americans, but African-Americans as well. Valmor came out on top, its dominance of the black cosmetics industry “signaled the end of an era (that) promoted beauty as a means of racial pride and “adjustment.”

There’s no written explanation why Neumann decided to do all the artwork for Valmor Products himself – probably because it was too expensive during the 1920’s and ‘30’s to contract another company or artist to do something he could do himself. 
It goes without saying Neumann’s designs have lived long after the demise of Valmor – and his own life. But for many, the empire he created will continue to live on in numerous discussions about art, the psychological complexity of advertising, and how capitalism benefited from racism.