My main character is an artist (painting) who recently lost her 4-year-old son (he didn't die, he just disappeared or got kidnapped, she doesn't know) and has been kind of depressed and alone ever since (the father is gone). How can I let one remarkable painting of her son naturally recur in the story multiple times? I want it to be a motif. Also, can someone tell me how artists sell their paintings? Do they have an agent and how does it work with commissions? How about other jobs?
Well Maybe the painting could be hanging on the wall and your character passes it every time she enters the home. Maybe your artist have a room specifically for her painting and she has the painting sitting in there on an easel. Maybe it's above a fireplace or in a dining room or maybe she has it in a museum that she got to buy her paintings. Maybe she got permission to do street art and it's on a wall somewhere or maybe she has it painted on a wall in her place. The possibilities are endless, just think of what would continuously grab your attention to a painting. Where would it be? Would it be hanging and if not how is it making itself noticeable to you constantly?
As for the question of how painters sell their artwork, there can be a few different ways depending on which approach they want to take. I've provided some links for you and if these don't help, there are a few results in google search.
http://www.artpromotivate.com/2013/02/how-do-artists-sell-their-art.html
http://www.wikihow.com/Sell-Paintings
http://answers.yahoo.com/question/index?qid=20110205173303AAX2ZaI
I hope this helps!
-Maria