The problem with idols is that they are not transparent enough. Idols eventually stop, struggling to lead anywhere transcendent or worthy of it. Bad art is similar; too heavy with the presence of the artist, their 'message', emotion, (or whatever) thrust upon us. Good art, in contradistinction, requires the self-dispossession of the artist, allowing the completed work to be neither untrue to the 'stuff' of the piece of art (whether words, clay, canvas, etc.) nor the world it speaks to and out of. Beauty is unveiled in a work of art when, in the depths of the artist where artist and transcendence meet in the metaphor of the creation, what is 'more' in the work is released and made manifest in its creation. This is why the artist and her work is a great metaphor for the God-world relationship, with particular applicability to the Christian conception of creation with its sensitivity to the freedom and integrity of creation. (See Rowan Williams, Grace and Necessity; here for a helpful review.) In the Christian schema of things the 'artist' of creation is the trinitarian God of Father, Son and Spirit, the dance of complete self-giving that is a union of love. The Father self-donates all that the Father has to the Son, and the Son gives all in return in the Spirit. And from this union that is love creation is made with its own substantial (although contingent) form, beauty and integrity.
This metaphor of artist and work of art is also helpful when considering the Incarnation - the Word becoming flesh - of the Son of God as Jesus of Nazareth. Jesus is not an idol, for he is the work of the self-dispossessing God of Father, Son and Spirit; indeed, he is the Son in the flesh, whose only identity is to be found in relation to the Father. There is 'space' in Son, both for the 'stuff' of the work (human flesh) and its relation to the world, and the 'more' who is made visible in him, the Father. (See John 1:18).
[The picture is from Frederick Hart's creation sculptures in the Episcopalian Washington National Cathedral.]