It is my belief that we are unique, but only about 0.1% of each of us is what makes us unique. The other 99.9% we share and can use to draw some understanding of each other. I do not feel that we can completely understand each other due to the 0.1% wild card acting as a multiplier.
Absolutely. It is through shared experience that Photography generally works and it is the fact that we are all so alike which gives me hope for developing at least a rudimentary framework.
The main thing that is wrong with your thinking is to consider the Photograph as containing language, or that it is capable of being structured like language.
Images work through systems much deeper and, in some respects, more rudimentary than language. All animals with vision work with visual cues and it is from this system that language developed. Language is representational and it's usefulness is what has caused it to overlay and supercede the visual.
The word 'rose' for example represents an ideal. We all have an image of a rose that the word conjures up (and for the majority it's red) - it is a metaphor.
But a photograph of a rose is something else. It represents both all roses and one specific individual (the rose in the image) at one and the same time. It is because of this that a photograph could be said to contain too much information*. Which is one of the reasons that B&W photography is considered more 'arty' than colour. That and the fact that a colour photograph is too 'real'.
All this aside, any attempt to codify the system of signs (those signals within an image that trigger our various responses) must start with defining all of the elements that can play a part.
Light and colour are two immediate ones. There are different qualities of light and these can be further modified (in colour photography) by colour temperature, and in all photography by direction.
We will have a different set of responses to an image shot in morning light (quite blue), at mid-day (yellowish), evening (orange), fog and so on. That is because they represent times of day and weather conditions that we have associations with. And we haven't even started with artificial light.
Then shadows will play a part. Shadows have a variety of functions in an image from providing surface texture to giving an air of mystery or oppresion.
Body language, facial expression, composition.... And each will modify the others. A person reclining on the grass in the evening will have one set of cues, the same pose on a bed will give another set, and a third if we position the body on a sofa.
It appears a daunting task but I think with a lot of careful thought we can analyse it down.
Ralph Gibson has done some interesting images that might help people understand where we are going.
http://www.ralphgibson.com/gallery/
*In this instance I use 'information' in the sense of telling us about the surface appearance of things.