Aesthetic: a particular theory or conception of beauty or art : a particular taste for or approach to what is pleasing to the senses and especially sight.
The mind is constantly trying to organize and make sense from visual information. Analysis of the spatial relationship of visual elements, recognition of identifiable shapes, and path of eye travel when viewing a photograph all lead to a sense of visual structure.
Photography- Bruce Warren
A picture is what it looks like.
Looking at Photographs-John Szarkowski