Contrast is such a powerful tool that many pictures derive all of their interest from contrast alone.
Click to see all of the pictures in this post bigger.
This picture works by playing on simple yet powerful contrasts. Tall against short, contrast of shape and rough texture against smooth texture. Any picture with one character looking at something can work very well by creating a kind of "closed circuit". The viewer's eye travels back and forth between the character's gaze and what the character is focusing on. Check out how great the balance of shape sizes is: there are a great variety of small medium and large shapes and areas of detail balanced against big open blank spaces. The contrast of that big open overcoat to the small cigarette, ashes and wisp of smoke is really exciting to the eye.
These things all work so well that Tom breaks one of the most basic rules of composition: never have two objects that are equally weighted in the same frame.
Having two equally weighted things in the same picture divides the viewer's interest and flattens out the picture because both sides of the picture have the same emphasis. So if you have a picture with just two things in it you should always make one more dominant and one lees dominant. Like making one higher than the other or one more towards the center and the other off to the side.
When you do this, you want to be careful that you don't break the other most basic rule of composition: Don't ever put anything in the exact center of the picture frame, because, again, that divides the space into two exactly equal halves and flattens everything out.
Back to the rule about two evenly weighted objects: artists break this all the time for the purpose of showing how similar or how different two things are. If you put two things exactly side-by-side it's a clear cue to the viewer to compare and contrast those two things. Political cartoonists do this all the time.