Ask whether there is a section of the frame that changes your sense of the portrait when viewed on its own. Look for a detail that gives the portrait a different character when you notice it.

A framed view of a portrait subject
A portrait from this sequence
A featured study of a portrait subject
A moment to pause in the gallery
A portrait with attention to the space around the figure
A portrait alongside the other selections
A study in how a person is framed
A portrait chosen for the gallery sequence
A gallery portrait to consider as a whole frame
An entry in the gallery