1. An image generating apparatus comprising: an image selecting section configured to select an image as a reference image; an extracting section configured to extract at least one related image which is related to the reference image selected by the image selecting section; a generating section configured to generate a new composite image by using the reference image selected by the image selecting section and the at least one related image extracted by the extracting section according to a layout, the layout comprising a definition of at least one kind of information selected from a group comprising a background image, the number of images to be used to generate a composite image, a size of each image to be used to generate a composite image, and positional relation among images to be used to generate a composite image; and an instructing section configured to issue an instruction to make the image selecting section select an image which is being displayed on a display screen as the reference image and make the generating section generate the new composite image based on the selected reference image.