A method comprising: examining a received image and detecting a subject depicted in a subject portion of the received image (306, 308), wherein the subject is a face of a person depicted in the received image, and the subject portion is a face portion of the received image; detecting one or more depictions of one or more previous-image subjects in one or more previously-stored images stored in one or more image collections, wherein the one or more previous-image subjects correspond to the subject of the received image; determining a likelihood that the subject portion of the received image will be used as a replacement to be inserted in place of one or more corresponding subject portions of the subject in future images examined at a later time, wherein the likelihood is determined based on one or more characteristics of the one or more previous-image subjects in the one or more previously-stored images, wherein the determining the likelihood comprises determining a historical relevance as a frequency and a recency of appearance of the one or more previous-image subjects in face portions of the one or more previously-stored images; storing (318, 322) the subject portion of the received image, or a reference thereto, in an image cache in response to the determined likelihood being greater than a threshold, the image cache being different than the one or more image collections, wherein the image cache is available to be searched for the subject portion of the received image and one or more other face portions of images to replace corresponding subject portions of future images; examining a new image and detecting a new subject in a new subject portion of the new image, the new subject corresponding to the subject of the received image; and if a quality score of the subject portion of the received image in the image cache is greater than a quality score of the new subject portion, replacing the new subject portion in the new image with the subject portion of the received image. examining a received image and detecting a subject depicted in a subject portion of the received image (306, 308), wherein the subject is a face of a person depicted in the received image, and the subject portion is a face portion of the received image; detecting one or more depictions of one or more previous-image subjects in one or more previously-stored images stored in one or more image collections, wherein the one or more previous-image subjects correspond to the subject of the received image; determining a likelihood that the subject portion of the received image will be used as a replacement to be inserted in place of one or more corresponding subject portions of the subject in future images examined at a later time, wherein the likelihood is determined based on one or more characteristics of the one or more previous-image subjects in the one or more previously-stored images, wherein the determining the likelihood comprises determining a historical relevance as a frequency and a recency of appearance of the one or more previous-image subjects in face portions of the one or more previously-stored images; storing (318, 322) the subject portion of the received image, or a reference thereto, in an image cache in response to the determined likelihood being greater than a threshold, the image cache being different than the one or more image collections, wherein the image cache is available to be searched for the subject portion of the received image and one or more other face portions of images to replace corresponding subject portions of future images; examining a new image and detecting a new subject in a new subject portion of the new image, the new subject corresponding to the subject of the received image; and if a quality score of the subject portion of the received image in the image cache is greater than a quality score of the new subject portion, replacing the new subject portion in the new image with the subject portion of the received image.