Look at the space around the subject and see how it affects the rhythm of the image. If the portrait shows a gesture, consider how much of its effect depends on the surrounding space.

A gallery image framed around a portrait subject
From this set of portraits
A person portrayed in the image collection
An individual frame from the gallery
A portrait presented with the gallery images
A frame to view in context
A portrait from a collection of figure studies
A portrait presented in sequence
A gallery portrait with the figure as its focus
One view from the collection