The pastel above does not show the entire subject. The sheet of PastelMat it is painted on is pure white and highly visible in areas surrounding the image. Some areas of the painting are more detailed that others. Yet the painting is finished, I will not do anything else to it. How can that be?
The answer is simple–when you are done, you are done. Done means something different to every artist, there is no rule (and if there were who cares anyway) that says you must cover your entire ground, you must have the same level of detail throughout (this actually can ruin a painting), or that you must include everything you see about your subject. A good painting focuses in on what draws the artist to the subject in the first place. That may be a literal characteristic or an abstract idea. If everything is the point of focus, nothing stands out.
In the example above, I was interested in the light and texture of the flowers growing in a garden. I wanted to create the essence of movement and energy from sunlight on flowers on an early autumn day. By using the white of the paper (as I would in watercolor) as a design element, I was able to get a light, airy feeling into the piece which would have been totally lost had I covered the entire sheet with the image. If I had added some texture to the dark green area at the top right section of the image, I would lose the strong contrast that creates the sense of light on the pink flowers in that area.
So, to answer the question “what is finished?”, you have to ask yourself if the painting is getting the message of what attracted you to the subject across. Do this throughout the painting process, as soon as you say “yes”, you are done. No one can answer that question but you, the artist. So many times students will ask me “am I done?” (or “can I be done?”) , I cannot give them an answer because it is not my painting. Only the artist knows what they want their work to convey.