I decided to not elaborate on that because the second-order effects depend on why everyone has more money. If it's because everyone is more productive, then there's also lots more art floating around, because the artists are also more productive. I do agree that people who are richer spend more money on luxuries like art, but it's not clear to me that all ways of giving people more money actually make more rich people.

But even if there's a bunch more art floating around, there is a fixed supply of the best original paintings, and those will still go to whoever wants to spend the most money at art auctions. (Of course, best is subjective, and so on, but that's part of the point of using auctions.)