In most cases, it is not worth the time and effort in a short presentation to take the audience through a demo or a series of screenshots of your application. At this stage in the pitch process, understanding the exact flow of your application is not critical.
What can matter though is the simple question of whether you have a decent product or prototype or not. The role of a screen shot here is not to show the exact detail of your app, but more a proof point.
One way to make this point is to use an office background with some screens, and paste a number of screens on the monitors. That’s what I did in a recent deck for my other venture 9xchange. I made the office background black and white, to make the screens pop a bit more.
(Look how I managed to Photoshop the screen shot behind the standing desk light)