What is a photo? One thing is sure - it is not a 3D image even if it is representing a real-world 3D scene. It is a flat 2D plane - yet we interpret it as a 3D representation, because we are well practiced in making this connection, this mental leap from the 2D image to the 3D world, that almost all images represent.
With some of my images, I have deliberately attempted to increase the impact of an image through reinforcing the strength of this connection between the 2D representation and the 3D reality behind. Things can be done (at both the taking and making stages) to increase the sense of depth, to HELP the viewer make the mental leap. The 3D relationship between parts of a picture have to be carefully considered, the maximum use made of shadows, this is crucial to the impact of an image.