I want to emphasize that the question of the subjectivity of beautyis distinct from the question of whether there are rules or principlesabout beauty. Many aestheticians are particularists. They believe thatthere are no general rules or principles governing what makes thingsbeautiful, and that what may count towards beauty or aesthetic merit inone context may be aesthetically irrelevant in another context (or mayeven count against overall beauty or merit). But this is consistentwith such a view that judgments of beauty are more than merelysubjective.
Kant is famous for having arguing that there can be no rules or principles of taste in his Critique of Judgment.Interesting contemporary discussion of the possibility ofgeneralizations regarding beauty and artistic merit can be found inMary Mothersill's book Beauty Restored. Mothersill isskeptical of there being any interesting generalizations here, but I'mnot convinced by her arguments.
What about the principles of design that are mentioned in the question? Particularists will think these are just rules of thumb--useful but ultimately inaccurate generalizations. I'd be interested in finding out whether there was evidence that they are accepted cross-culturally. If they were, there might be some reason to think that there was some broadly evolutionary explanation for them. In the end, the question of why certain generalizations about beauty and our visual preferences are true--if they are true--seems to me to be an empirical question. That is, the answer to it would await serious scientific investigation.
It isn't quite right that we see no difference between a flower or a bunch of flowers and a standard still life. For example, we see paintings as largely flat, and we take notice of their painted surfaces. This distinguishes our experience of them from our experience of flowers. More importantly, we typically value the two sorts of objects in different ways. A still life might be valued because of its beauty but also because of the skill of the painter, its capacity to express and evoke emotion, what it symbolizes, and/or the perspective on the world it manifests. That is, we value paintings as works of art, not as mere aesthetic objects. (Beauty is not our only concern when we look at paintings of flowers.) While we sometimes value bouquets of flowers for what they express, the art of flower arrangement does not seem to have the rich capacity for expression and meaning that painting does. The same is true for mere bunches of flowers.
So the answer to your original question is no. Merely being intentionally drawn does not make something beautiful (for one thing, there are ugly still lifes), nor need successful still life involve a degree of beauty that cannot be found in a single flower or arrangement of flowers. But there are reasons to think that there are values to be found in great works of visual art that are not to be found in a flower in a vase.
However, following up on Richard's point about meaning, consider two similar sounding words:
a) gorgeous (for gorge)
b) excrement (for exquisite)
Does 'gorgeous' sound as ugly to you as does 'gorge'?
Does 'excrement' sound as pretty to you as does 'exquisite'?
I think that while there might well be words that sound pretty no matter what they mean, there is often an attaching of meaning (or content) of a word to its experienced aesthetic quality (ugly, pretty).
Yes. Some aesthetic questions are about natural beauty, and the notion of medium does not apply in the natural context. There are philosophial questions about artistic genres (e.g., how do horror and suspense work?), and it may be worthwhile to consider those independently of the specific media in which those genres are instantiated. Philosophical investigation into the objectivity of aesthetic and artistic value seem largely independent of concern for medium. Also, an overemphasis on medium can be misleading. For example, film and television are plausibly different media, but they function in very similar ways. It can be useful to think of them as two species of a larger category (the moving image).
There's plenty of room left for traditional art. Why? Because the arts aren't really in competition for room. Painting can give accurate images, represent an imaginary world, use symbolism, etc., but that doesn't mean there isn't room for sculpture, literature, photography, film, theater, dance, etc. Why wouldn't there be room for them? If it were the case that each art had a distinctive function, then it might seem that the invention of an art that could perform all artistic functions would render those other arts superfluous. But this would be mistaken. Swiss army knives haven't rendered screwdrivers and bottle-openers superfluous. Moreover, the individual arts don't work like that--they don't each have distinctive functions. Each one of them can do a variety of things--and it is up to artists to show us what can be done while working in those forms.
Philosophers definitely are interested in the role that qualia play in the aesthetic experience. There have been a bunch of articles on this (and related) subjects in The Journal of Consciousness Studies over the last few years, including a dedicated issue on "Art and the Brain." You might also look at works by Gregory Currie, Dominic Lopes, and Cynthia Freeland.
Your question has many dimensions. First of all, it might be taken as asking why our species seeks out beauty while others do not. If that is the question, then one point to note is that it might be the case that other species seek beauty as well. For instance, males in other species of animals produce exotic ornamentation in order to gain an advantage with females in sexual selection. Do those females seek out beauty? I would be hard pressed to show that they don't.
Second, and leaving that question aside, one might take this question as asking why we like things that are beautiful. But if you reflect on that for a moment, it might seem a bit strange. Imagine someone trying to figure out why we don't like pain. Perhaps all that can be said is that painful things hurt, which by definition we don't like. On the other hand, assuming that beauy is pleasant, one may still ask the question: Why do we find beautiful the things that we do? For example, anthropologists, psychologists and aestheticians are curious why we find some human faces beautiful and others not, such that even though there's some cultural variation there seem to be some universals as well. Are we "hard wired" to seek out symmetry, for instance, in faces? If so, why? One suggestion is that symmetry is a sign of health, and thus an indicator (not guarantee) of good genes. The notion of Fluctuating Asymmetry is used in evolutionary biology to refer to a measure of a potential mate's viability.
Of course, all this has no obvious application to inanimate objects, which are part of your question. On the other hand, some would hold that we can explain what is beautiful about a building, a painting, or a symphony in terms of a single condition that applies to the human case as well. For more on this see George Dickie's clear and insightful book, _Evaluating Art_.
I'm not convinced that the golden ratio really is aesthetically pleasing to humans. See a special issue of Empirical Studies of the Arts (Volume Fifteen, Issue Two), 1997, which has a number of articles in it that challenge the idea that the Golden Ratio (or Golden Section) is really pleasing/preferred.
What a can of worms! To my mind, the most interesting philosophical work on the subject is David Hume’s wonderful essay “Of the Standard of Taste”. Humeargues that there are a number of criteria for what counts as being a‘true judge’ of the arts (that is, someone who has good taste). Here’s Hume summing up his account of true judges in that essay: “Strongsense, united to delicate sentiment, improved by practice, perfected bycomparison, and cleared of all prejudice, can alone entitle critics tothis valuable character…."
Hume’s views (although they are controversial) seem pretty plausible. For example, it does seem that practice with—and experience of—a form of art is crucial to being a good judge of it. Prejudice (e.g., an unwillingness to put aside one’s own personal concerns) may certainly keep one from being a good judge. Areasonable degree of intellectual capacity (as exemplified in acapacity to grasp the nature and point of works of art) certainly seemscrucial to being a true judge of many forms of art, and this seems tobe what Hume is getting at in his mention of ‘strong sense’. Andhaving an ability to discriminate between subtle aesthetic differences(what Hume calls ‘delicacy of taste’) seems important too.
All that being said, it is surely the case that many claims about ‘bad taste’ are just posturing.