Figurative art encompasses many things; mystery, mood, gesture, portraiture and the human body, in part or as a whole. It explores the human form in all its dimensions. Figurative paintings include portraiture as well as both clothed and nude figures in every conceivable style, from minimalism to modern realism. With such a variation in images, what makes one portrait stand out from others?
I find that there are elements common to really powerful, beautiful portraits. Structure or a good composition is essential, something that really grabs the viewer's eye and makes them want to look further at a painting. What does this involve? Design elements such as shapes and colors and their placement relative to one another is important, as is light and shadow. These are the things that draw us in for a closer look because they create interest and grab our attention. They make us curious. Details are also important. The way the light is reflected off a pearl necklace, the expression in a face, the paint peeling off a decaying building in the background... attention to subtleties are an important factor in conveying the overall statement.
Leave out anything that doesn't enhance the composition. My theory is that if it doesn't help the composition, then it will make it weaker. Proper use of light and shadow help to define the shapes and lines in the painting, express an emotion, and are critical to making a portrait stand out as being technically sound and aesthetically beautiful.