The U.S. Postal Service receives about 50,000 suggestions for new stamps every year. Many are eliminated because they do not meet the basic rules for what can be on a stamp. The major guidelines:

1. U.S. postage stamps will primarily feature American or American-related subjects.
2. No living person may be honored by portrayal on a stamp. Former presidents can be honored the year following their death; other people after 10 years.
3. Events of historical significance will be considered only on anniversaries in multiples of 50 years.
4. Only events, persons or themes of widespread national significance will be considers.
5. Stamp will not be issued to honor cities, towns, municipalities, counties, primary or secondary schools, hospitals, libraries, or simular institutions.
6. Stamps commemorating statehood will be issued only at intervals of 50 years from the state’s first entry in the Union.
7. Stamps will not be issued to honored institutions or individuals whose principal achievements are associated with religious undertakings or beliefs.
8. Commemoration of universities and other institutions of higher learning will be done only via stamped postal cards issued on the 200th anniversary of the institution’s founding.
9. No stamp will be issued if one covering the same theme has been issued within the past 50 years, except for traditional themes such as national symbols and holidays.

-- Associated Press