1. An image processing method for adding decorative frame images to a plurality of input images individually, comprising: (a) acquiring a representative color for each of the input images by analyzing image data representing the input images; (b) selecting a decorative frame image to be added to each of the input images from a plurality of decorative frame images based on the representative color for each of the input images; and (c) generating an output image by individually synthesizing the decorative frame images with a same image pattern and the input images, wherein the step (b) includes selecting a plurality of decorative image candidates based on the representative color of each input image so that if the representative color for each of the input images is similar then a plurality of similar decorative image candidates is selected for all input images, and if not then the plurality of decorative image candidates is selected for each input image, displaying on a display a selection screen allowing a user to select the decorative frame image from the plurality of decorative image candidates, and recording a command history related to selection of the decorative frame image by the user, the plurality of decorative image candidates is selected based on the command history, a representative color of each decorative frame image, and the representative color of each input image, and each of the steps of the image processing method is executed by a microprocessor.