Van Gogh was not a deep thinker, nor did he put a lot of deep meanings into his work. His work followed the Impressionists, who were working from an idea of mixing and applying paint at face value. Now, further back in art history, during the Renaissance and even the some of the movements in between dealt with meanings within the arts. But, by Van Goghs time, he was dealing directly with color theory that he was learning from the Japanese prntmakers that were becoming popular in Europe at that time. But, as far as "meaning" within the work, it was merely life, emotion, and the human condition.
He had no intentions of conveying a meaning to a pipe... but by the time the Surrealists developed, meanings in art started to become more interesting.
But, low and behold, Van Gogh was just making pretty pictures.