How you cite an image will depend on which citation style you are using. However, the basic information you may need includes the following:
If you found the image in a book, you will also need the author, title, publisher information, date, page, and figure or plate number of the reproduction. If you found the image online, you will need an access date, the web site address (URL), and, in some cases, an image ID number.
Some professors will ask you to create a bibliographic entry for each image used in a paper. Others will prefer that you include relevant citation information within an image's caption (right under the image). If citing images as a bibliographic entry, follow the general rules of citation for either a still image or a film, for Chicago or MLA style.
There is no absolute standard for captioning images. However, consider the following examples (from Sylvan Barnet, A Short Guide to Writing About Art):
Captions should be numbered consecutively. Since authors are responsible for obtaining reproduction permissions, captions will reflect the institutions' requirements and those of the photographer. Provide the shortest possible form: by the gracious permission of Her Majesty the Queen [equals] by permission of H.M. the Queen.
1. Castiglione, Crucifixion. Genoa, Palazzo Bianco (photo: Frick Art Reference Library)
2. Pietro Bernini, Bust of Scipio (or Scipio). Rome, S. Giovanni Dei Fiorentini (photo: Davis Lees, Rome)
3. Attributed to Cherubino Alberti, engraving after Florence Cathedral Pieta, ca, 1572. Vienna, Albertina (courtesy J. Held)
4. Parthenon, east frieze (detail) (from A. Smith, The Parthenon, New York, 1975, pl. 2)*
* include reference to this book in your bibliography
5. Tree of Vices, Le Verger de Soulas, northern French, ca. 1290. Paris, Bibl. Nat. MS fr. 9220, fol, 10r (photo: Bibl. Nat.)
6. Roman sarcophagus, Death of Meleager (detail). Paris, Louvre (photo: Alinari)
This is another example of a citation, from ARTstor's website:
Haystacks. Claude Monet. 1890. In ARTstor [database online]. [cited 22 October 2004]. Available from ARTstor, Inc., New York, New York.