I really like picture #2 of the panda.  The Gestalt principle tells us that our eye will make connections.  In this photo our eye connects the both the back of the panda as well as the top of the pandas head.  It is very neat that we make these connections without even realizing it.  This principle is called closure and deals with both the negative and positive space of the image.  The positive space is the black and the negative space is the white and connects the background to the panda as well. The lines also are used to make the panda almost look like it is popping out of the page.  It is very cool how they use closure with the panda to come up with a very unique image.