1. A display system, comprising: an image display device having two or more sets of images for display; a display screen; a camera configured to be directed toward positions adopted by user viewing said display; a face detector configured to detect human faces in images captured by said camera, said face detector is configured to detect faces in at least two face categories, and to detect a dwell time respect to each detected face, the dwell time indicating a time period during which a detected face is oriented towards the display screen; a selector configured to select, responsive to a frequency of detection of categories of faces by said face detector with respect to one or more different periods, a set of images to be displayed on said image display device at that period, wherein said selector is responsive to face category frequency data detected during a corresponding previous period, said previous period being a predetermined time interval; and a statistical analyzer configured to determine a frequency of detection of categories of faces in at least one of an age or a gender category over the predetermined time interval, wherein the selector is further configured to select a promotional display sequence stored on a data storage device and including advertising images for products or services, based on a relative frequency of detected faces in each of a different category.