It would be nice if the tray icon gave a visual cue of the Mode. I always forget to switch back from Presentation Mode to Normal after watching a movie. Alternatively, a setting which resets the Mode from Presentation to Normal after a certain amount of time would be great.
There are no standard icons to do this and frankly, fitting in such an indicator into the already crammed battery-icon (which shows the battery, the load-status and whether it's plugged-in) at 16-24px isn't a good idea. Also, setting the mode to normal after a timeout seems total overkill. Your mediaplayer should inhibit the screensaver itself during playback and then re-enable it. Just imagine the scenario of doing a presentation and because it takes longer than anticipated, the presentation mode switches off and the screensaver kicks in. So marking this as wontfix.