During the 1930s, in addition to working for the NSS, Schomburg freelanced with Better Publications, producing interior line art for Thrilling Wonder Stories and other of the company's pulp magazines.

His skill at drawing anything mechanical soon had him illustrating aviation covers for Flying Aces and electronic equipment for the Hugo Gernsback pulp Radio Craft.

[11] In the early 1950s, Schomburg left comics and spent the remainder of his career on covers and illustrations for science fiction magazines, astrology publications, and books, including the Winston juvenile series.

[11] In 1977, Schomburg and a few of his fellow Golden Age comic book artists collaborated on the Invaders Annual #1, written by Roy Thomas.

[12] Stan Lee wrote: I've always felt that Alex Schomburg was to comic books what Norman Rockwell was to The Saturday Evening Post.

... [D]espite the quantity of work we gave him, despite the care and effort that went into every Schomburg cover, I cannot remember Alex ever being late with any illustration.