A recent question concerning the president putting himself on the dollar got me to thinking: The US dollar at one time was printed with an appearance to celebrate aspects of education. I'm wondering if there are laws nowadays that require the dollars to depict significant historical figures like presidents, or if this sort of educational use for the appearance of US dollars is still possible under current law. In other words could the Secretary of the Treasury simply order the commissioning of such an "educational series" nowadays? Are nationalist political concerns pushing a mythologizing of the founding fathers the only thing preventing this?
The Secretary of the Treasure is granted authority to specify the design under section 16 of the Federal Reserve Act (1913), however some legislative restrictions are presented in 31 U.S. Code § 5114:
United States currency has the inscription “In God We Trust” in a place the Secretary decides is appropriate. Only the portrait of a deceased individual may appear on United States currency and securities. The name of the individual shall be inscribed below the portrait.
The Treasury FAQ says:
Why were certain individuals chosen to be pictured on our paper currency? As with our nation's coinage, the Secretary of the Treasury usually selects the designs shown on United States currency. Unless specified by an Act of Congress, the Secretary generally has the final approval. This is done with the advice of Bureau of Engraving and Printing (BEP) officials.
The law prohibits portraits of living persons from appearing on Government Securities. Therefore, the portraits on our currency notes are of deceased persons whose places in history the American people know well.
The basic face and back designs of all denominations of our paper currency in circulation today were selected in 1928, although they were modified to improve security against counterfeiting starting in 1996. A committee appointed to study such matters made those choices. The only exception is the reverse design of the one-dollar bill. Unfortunately, however, our records do not suggest why certain Presidents and statesmen were chosen for specific denominations.
From a practical standpoint, a new "educational series" with different portraits seems unlikely. Lobbying from business interests with investments in bill recognition technology is probably the biggest impediment. Such lobbying has played a part in similar decisions in the past, including the current generation of coins, where ensuring electromagnetic compatibility with silver coins was a significant goal.