How to sync up the experience for large number of users of a web app?
dxjones: First, you need each instance of your running web app to be synchronized to the same clock, so they can make events occur at the same time.Second, it would probably be best to upload your images from your server to your 1,000 clients before they need to be displayed.  This can be done asynchronously, so you server doesn't struggle to get it all done within a few seconds.Third, your web app clients could handshake they received the images, ... or you could just allow enough time to pass so you are confident they all have the images, ... and then they could all flip their displays at a pre-arranged time.Voila.  Synchronized image display.