Vanity paintings, like the readings from Ecclesiastes, focus on the transient nature of life and the fleeting nature of natural beauty. In paintings, they may show cherished hobbies, an opened book, a burned out candle, flowers (sometimes past their prime or dying), a half-eaten meal and many times (in case we miss the point) a human skull.
Our belief in eternal life and the permanence of heaven, make vanity scenes nostalgic and sad, but not tragic.