Well, one interesting thing I found out about the topic: You get the hits you want if you spell it with the leading "a" (i.e. aesthetics) rather than just "esthetics". Googling "esthetics" you get all these sites for beauty treatments, cosmetics, spa's etc. --- I guess the "beauty" industry is calling itself the "esthetics" industry these days!! I call it "gilding the lily", which only works of course if your lily is new and pretty...faded, dried-up lilies don't look any better covered with gold!!
Anyways I'm finding some interesting stuff on "aesthetics". The Trinity Foundation had a rather long paper on the topic by Gordon Clark ( Download 067b-ChristianAesthetics.pdf ), that was somewhat interesting and a little pompous. I don't agree with his assertion of music being lowest in the hierarchy of the arts, unless we are going from the concrete to the abstract. Music is often paired with words as poetry, prose, saga, etc., due to it's ability to accent and bring out the emotions and senses that are being communicated through language. None of the "arts" touch so much of our core as music does, affecting the heart, mind, and spirit.
Another statement of Clark's that I viscerally disagree with is: "In any case, a work of art need not be beautiful. The ugly can also be artistic." He states this in context of discussing how difficult it is to define beauty. My opinion is that if it doesn't strike one as "beautiful" in some sense, then it isn't art...regardless how "artistic" it may be. There's a whole landfill of "art" that can be described as "artistic", but is not beautiful by anyone's definition!! Usually it's funded by the government, or passed off by some Marxist who's trying to make a statement about some sort of "class warfare".
I don't think we necessarily need to define beauty, but I think we need to keep beauty in mind when discussing Christian aesthetics. One thing that stands out when we look at God's creation, it that it is "very good" or "beautiful". I would think we could define "bad" art as that which fails to have intrinsic beauty. Ugliness happens pretty easily and doesn't require any talent or effort to produce. Man since the Fall seems to have some propensities towards sin or ugliness. When we are focused on God, we seem more capable of righteousness and of creating beauty. I don't think Christians necessarily have a lock on this, by the way. I think the "general revelation" that is in every human being is able to inspire him towards beauty, and some people have a talent for this in spite of their lack of faith.
"And God saw everything that he had made, and behold, it was very good." Genesis 1:31