"Finally, brothers, whatever is true (ἀληθῆ), whatever is honourable (σεμνά), whatever is just (δίκαια), whatever is pure (ἁγνά), whatever is lovely (προσφιλῆ), whatever is admirable (εὔφημα) – anything that is excellent (ἀρετὴ) or praiseworthy (ἔπαινος) – think about those things."
Now, the things that are lovely (προσφιλῆ) are of course the standard subjects of conventional art:
The Matterhorn, seen from Zermatt, 2007
Miranda Kerr, model (photo by Ahmad Fauzi Abdullah, 2009)
However, for Christians, beauty is determined not simply by convention, but by the inherent worth of Creation ("In the beginning God created the heavens and the earth... And God saw that it was good" – Genesis 1) and by people sharing the image of God (Gen 1:27) as they themselves make things. The artist may therefore play the role of pointing out beauties that the casual observer may have missed:
Maurits Cornelis Escher, Puddle, woodcut, 1952
Rembrandt, The artist's mother as the prophetess Hannah, oil on wood, 1639
Richard Beck explores some interesting aspects of this theme in this 2008 blog post.