Has It Become Convention?

The US Postal Service did a really nice job with their Abstract Expressionist set of stamps they recently released.

According to the USPS release:
"Abstract expressionism refers to a large body of work that comprised radically different styles, from still, luminescent fields of color to vigorous, almost violent, slashes of paint. In celebration of the abstract expressionist artists of the 20th century, art director Ethel Kessler and noted art historian Jonathan Fineberg (Gutgsell Professor of Art History, University of Illinois at Urbana-Champaign) selected ten paintings to feature on this colorful pane of self-adhesive stamps. Kessler used elements from Barnett Newman’s Achilles (1952)to frame the stamps. The arrangement of the stamps suggests paintings hanging on a gallery wall."