Any working painter today who does commissions knows that the demand for custom work is not limited to what we think of as traditional, head-and-shoulder portraits. In fact, it is not limited to portraits at all, as usually defined. I define the term "portrait" a little more broadly than some artists do. I see a portrait as a representation of anything important enough for an individual to be willing to pay an artist to paint (or sculpt) it. That includes people of course (still first and foremost), but also beloved pets, prized animals, homes, farms (flirting with landscape painting), and quite often various collectibles (which begins to involve still-life painting). Among the most often painted portrait along this line is that of various means of transportation. I once painted a portrait of a supersonic transport (SST) taking off. Add to that the "planes, trains, and automobiles" and you have a huge area with a very demanding clientele.
In the nineteenth century, such transportation portraits were mostly limited to ships, and if you want to get technical, horses. Surprisingly however, there was also a demand for paintings of trains as well. Turner is an example, though it stretches the definition well past the breaking point to call his 1844 classic, Rain, Steam, and Speed--the Great Western Railway a portrait, this work may well be the first painted depiction of this early transportation invention. The Impressionists also painted trains, again not as commissioned portraits usually, but detailed enough to be recognisable models. If all these transportation "portraits" have anything in common, it's that they all depicted the outside of the movable mass. Almost all, that is, except one by an exceptional French artist named Honoré Daumier.
Daumier was born in 1808, and is remembered more for his talent in etching, drawing, and caricature (which he practically invented in the sense we know it today). However he sometimes painted, and one of his best known is his 1863-65 painting, The Third-class Carriage. As mentioned before, it's not the outside of the train, but the inside, emphasising with great sympathy, simplicity, and honesty the nobility of the lower classes as compared to the "nobility" of the nobility. Daumier, as a caricaturist, was a "people person." Faces fascinated him. The fact that these faces densely populate a nineteenth century rail carriage is almost incidental. The colours tend toward warm reds and browns, warm blacks, with a few dashes of blue-green. Facing the viewer is a mother with a toddler sleeping in her arms, what appears to be her mother, and an older sleeping child next to her. Behind them, is a cross-section of "polite" French society painted with harsh, spontaneous, angular brushwork, contrasting with the soft ovals of the "third class." The masterpiece makes a subtle social statement heavy on family warmth juxtaposed against the cold, glaring, staring, unpleasantness of those from the "right" side of the train tracks.