Beall was technically skilled. He almost had to be, considering that he was usually working in what I consider the most difficult medium of all: watercolor. And he did better than many illustrators, being featured in advertising campaigns for Maxwell House Coffee (a leading brand for many years), doing cover art for Collier's magazine (a leading general-interest publication) and illustrating government posters supporting the World War 2 effort. Nevertheless, so far as his career can be evaluated, fairly or not, he probably should be rated as a second-rank illustrator.
Below are examples of his work, some of which I consider really nice.
I really like this illustration. Interesting composition and content -- very 1931-32. But Beall's treatment of the gal with the top hat is smashing. Well, the hat is way too large for her head -- but look at that face!
A poor quality image, but it is significant. For one thing, Beall uses the old trick of creating an overarching image made up of smaller ones. Another example is directly below. The main subject here is Franklin Roosevelt, whose first inauguration took place around the time this Collier's issue was on the news stands. The featured author is George Creel. He was Woodrow Wilson's propaganda / public relations supremo during the Great War. His son, also a George Creel, was in charge of Public Information for 8th U.S. Army when I was stationed in Korea. Though I did PIO work for another command, I met him a time or two.