1. An image management apparatus comprising: a storage unit that stores a plurality of types of additional information assigned to a plurality of images; a calculation unit that calculates a feature quantity of each of the plurality of images; an additional information extracting unit that extracts, based on the feature quantity, one or more types of additional information of the plurality of types of additional information; a display control unit that generates one or more icons corresponding to the one or more types of additional information and causes the generated icons to be displayed on a screen; an input unit that receives input of a signal according to a user's operation; an image selecting unit that selects, from the plurality of images, an image according to the signal received by the input unit; and an additional information assigning unit that assigns to the selected image, when input of an operation signal associating the image selected by the image selecting unit with an icon selected from the one or more icons by the user is received by the input unit, additional information corresponding to the icon associated with the selected image, wherein: the plurality of types of additional information stored in the storage unit are different labels assignable by the user to the plurality of images, the additional information extracting unit extracts, based on the feature quantity calculated by the calculation unit for an image selected from the plurality of images, one or more of the different labels for the image selected from the plurality of images, the display control unit generates one or more icons respectively corresponding to the one or more of the labels extracted and causes the generated icons to be displayed on the screen for the image selected from the plurality of images, and the additional information assigning unit assigns to the selected image, when the input of the operation signal associating the selected image with an icon selected by the user from the one or more icons is received by the input unit, the label corresponding to the selected icon.