The Duke University Libraries have created several Digital Collections  of interest those studying advertising and many other subjects.
One of the links on this page is for Advertising and Consumer Culture. It contains several collections of advertisements in various formats, some dating back to the 19th century. Two examples:
Ad*Access  - "presents images and database information for over 7,000 advertisements printed in U.S. and Canadian newspapers and magazines between 1911 and 1955"
adViews  - "a digital archive of thousands of vintage television commercials dating from the 1950s to the 1980s"