Here are some links to online collections of historic photographs of Miami Beach (each link will open in a new window):
General images (both contemporary and historic) are available on the City Clerk's website.
Historic images, arranged by year, are also available on the City of Miami Beach's website.
Photos related to Miami Beach's role in WWII can be found on the Camp Miami Beach WWII site.
A document collection called Travel, Tourism and Urban Growth in Greater Miami is available on the University of Miami Libraries' Miami Digital Archive