If the image was found online, as part of a website, treat it like a Web Object:
Author AA, Author BB. Title of page or object. Title of Website. URL. Published Month DD, YYYY or Updated Month DD, YYYY. Accessed Month, DD, YYYY.
If the image was found in a book, journal article or entry in a database, do not cite the image individually but give the citation details for the book/article/etc:
Author of image (if given). Title of image. In: Author of electronic resource (if given). Electronic Resource Title [medium]. Version number (if given). Place of publication: Publisher; date of publication.
Example:
Arteriole and venule (slide 8.9). In: Gartner, LP, Hiatt, JL. Interactive Color Atlas of Histology [computer program]. Philadelphia, PA: Lippincott Williams & Wilkins; 2000.
Tables, Figures and Boxes are numbered sequentially, according to their order of appearance in the text and the type of figure (e.g.: Box 1, Box 2, Table 1, Table 2, Figure 1, Figure 2...)
For more extensive information, you can look in the chapter on Tables, Figures and Multimedia in the AMA Manual of Style.