In the example appbar on my Windows Phone application I can see this line of code added a button:
ApplicationBarIconButton appBarButton = new ApplicationBarIconButton(new Uri("/Assets/AppBar/appbar.add.rest.png", UriKind.Relative));
What I find interesting is that the icon is sourced from "/Assets/AppBar/". Are there any of the other standard Windows Phone appbar icons in there and if so is there a list or reference somewhere for me to use?
If you have installed visual studio then you can get these files from here
C:\Program Files (x86)\Microsoft SDKs\Windows Phone\v8.0\Icons