A system and related methods permit a group of two or more users to initiate a realtime message session online, and invite participants to transmit and share digital images and other media to a common viewer tool seen by all. The messaging session may be conducted via a message server which mediates the exchange of typed, spoken or other messages back and forth amongst participants. One or more users may assume control of the commonly displayed images, for instance in a slideshow or other viewer tool. Users can discuss the displayed images or other media in realtime. The participants may each view, save, store, print or otherwise use or manipulate the copy of the image or images as presented to them. Session control of the set of displayed images may be passed from one user to another on a voluntary basis, using for example a control token or other mechanism. In embodiments shared control may be used. Out-of-order rendering and other optimizations may enhance the response time to participating viewers.