Brangwyn is an artist that interests me greatly, especially for his work as a muralist. I posted about that aspect of his career here.
It seems that the Rockefellers were in the market for Big Name Artists to create murals for their huge, Depression-era project. Matisse and Picasso were approached, but weren't interested. Diego Rivera, the well-known Mexican muralist accepted, but he famously created a work of political propaganda that was inappropriate for its setting and destroyed.
So the Rockefellers dropped to their B-list, selecting Josep (José) Maria Sert and Brangwyn to paint huge, monochrome murals. Sert's murals are rather bombastic, and are better known than Brangwyn's because some are located in a large, open area. All of Brangwyn's are found on a side corridor.
Worse, Brangwyn's murals are not very good. He was an interesting colorist, but the Rockefellers apparently desired monochrome murals that would blend with the rich, late Art Deco interior architecture and decoration of the building. It is possible that Brangwyn was also losing his touch due to age.
When I was in New York City in September I made a point of tracking down his murals and photographing them. Unfortunately, lighting conditions and the comparatively cramped setting made it impossible to get decent photos. Still, I hope you will find them of interest.