Sacred, Secular, Idolatrous: three categories or two?

[last follow-up to this http://sharperiron.org/forum/thread-did-bob-jones-do-right-thing-when-i… query about sacred art and nakedness, esp. of Jesus:

I keep using the term “sacred art.” Now, when I use the term, I’m usually referring to a category of art—one recognized more by “family resemblance” than by strict rules—in which the subjects are significant not only for humane reasons, but for divine (theological) ones. I like to use Raphael’s Madonna of the Meadow and Rubens’ Helene Fourment and her Children as easy examples of the difference between “sacred art” and art in general, which we might call (without prejudice) “secular art.”

“Sacred art,” however, is unquestionably often most highly prized and practiced in cultures where it is believed to aid us in worship. This can happen in a variety of ways—for example, when most of the populace of Europe was illiterate, how were they to be taught and reminded of Christ and His life, death, and resurrection? Many of us spend much of our time reading and writing and talking about these things—others must have looked, and described, and remembered, and recited. “Sacred art” would then be something more than just “art with something religious in it.”

But then, we all also know that idolatry—which I understand to be the worship of an image which deceives, as when the Egyptian-styled golden calf was miscalled “the LORD that brought you up out of the land of Egypt”—is strictly forbidden. So is every picture of someone mentioned in Scripture idolatrous? or every picture designed to teach me about holy things, like the beautiful illustrated storybook my parents read to us from as children? or only those which portray deity? or only those which are established in competition with God as objects of prayer? Of course, it is this last point we find ourselves most often debating.

But what I hope you’ll respond to is my strong feeling that we really do need to be able to talk in terms of three categories, not just two. Else we seem to be saying that all art must be either secular or idolatrous!