Art as a Rorschach test? Never thought of it, but it is very very spot on!
Art lies in the "rules" some "intellectual cliques" set (I am referring to what is considered an all time classic piece of art).
But it also lies in the eye of the beholder. Everyone filters the stimuli from their environment through their experiences, their mood, their knowledge and education. For example: I was at the beach today, I found a little pond with frogs nearby, I took photos of creatures others find disgusting, but I kept having a smile of satisfaction on my face the whole time. For me, these little guys were a piece of art and I used them to make my art. See? Everything is so fluid and subjective (the way I see it).
The example with the frog pond is perfect. For instance, anything that is commonly perceived as disgusting or commonly feared, etc. will, when interpreting something, like a piece of art, be considered through its common interpretation (unless the creator's associations are known, and cared for or considered).
The same mix up is also made when interpreting dreams. Looking at general symbolism, instead of one's own.
The more someone is a classic representative of the species, the more clearly even their individual symbolism will be perceived by the interpreters.
This, of course, also presents a unique challenge.