Chris Howard at The0phrastus had an interesting post yesterday discussing the tension between the mental model of a work of art (the inspiration), and it's actualization (the work itself), to which I threw in my own $0.02. He's a writer, I did my doctoral work in music composition, so I was writing from that perspective. With the "purely imagined" arts, like novels and string quartets, the model comes directly from the artist's imagination, although of course there's a tremendous background of experience that comes before. The difference between the quality of the inspiration and the quality of it's realization is often heartbreaking.
It's a lot different with representational visual art. The model is a thing directly visible in front of the artist's eyes, be it a landscape, person, or a still life. With this mode of creating, the gross level of imagination occurs with the initial selection of the subject -- placing the pieces of fruit, posing the person, etc. I'm sure that there's a lot of refined selection and imagination that's involved during the actual execution of the painting, but it doesn't seem that way -- it's submerged in the process of what seems like "copying" the physical model in front of me. And it's probably better that way... during the process of painting, I am never consciously focused on any issues of imagination, but rather on the mechanics of producing the art; a craftsman-like approach, in fact. It's certainly more fun and less distracting. Maybe it just means I'm a better painter than I ever was a composer.