I prefer the classic ideas of Adam Smith in the Wealth of Nations. It is a complicated discussion but in essence wealth generates more wealth. the classic example is a wetland field that won't produce anything but if I spend the money to tile it and fertilize it, now it generates more wealth every year with crops.
Adam smith disliked government, lawyers, bankers and the arts because they consumed rather than produced. He did admit they are a needed part of society but MUST not be too large or the focus of activity.
Your example of the panting is exactly what obama is doing. He believes that spending money on anything generates wealth. It is very important WHERE YOU SPEND THE MONEY.
No, we wouldn't all be better painting pictures, any more than we'd all be better raising beans (while nobody built any houses or did anything else that was necessary). But that hardly means pictures are useless.
Pictures are luxuries. While they may not be strictly necessary for survival, it is the availability of luxuries which encourages those who would be able to generate more wealth than necessary for their own subsistence, to do so. If no goods were produced other than those strictly necessary for material survival, there would be a limit to the amount of wealth anyone could find it worthwhile to produce. If increasing one's labors would entitle one to more beans than one could possibly eat, but there weren't any luxuries for which one could trade the excess, would there be any incentive to maximize one's productive output?