how to add the white border and 'peeling' shadow to a photo in Pages?
I'm not sure it's the same effect you're looking for, but to apply different borders in Pages I followed these steps:


Place the picture where you want it in your document
Open the Inspector by holding CMD+I
Go to the Graphic tab:
  
Go to the Stroke menu and choose Picture Frame from the drop-down menu.
  
Now you can choose a picture frame and alter its appearance by using the Scale slider.