For large pictorial costume books, be sure to check the GT 500 call numbers in the Reference Room on the second floor of Gorgas. Here are some highlights:
Berg Fashion Library
This database provides both text and images on world dress and fashion throughout history. Content includes the Berg Encyclopedia of World Dress and Fashion.
This is a complete searchable archive of American Vogue from 1892 to the present. Every page, including cover, ads and fold-outs, is included. This is a great resource for costume designers.