POSITIVE and NEGATIVE SPACE
The success of your portrait depends on your utilizing positive AND negative space in an effective manner. But what are these two things? POSITIVE space is the 'actual stuff' in a picture, NEGATIVE space is the 'white' or inactive space with 'nothing' in it. Sometimes less is more, and you can say a lot with 'nothing.' Such is the case here.
Another way to think about positive and negative space is in terms of 'FIGURE/GROUND RELATIONSHIP', one of the components of Gestalt theory listed on pages 126-127 in Basics of Design. Our dingbat project touches on other components of this theory as well: PROXIMITY and SIMILARITY, which both essentially say that if you group stuff together, people will see it as a whole object--ie, like the DINGBATS we are using in the positive space areas of your portraits.
Here are some links to check out:
POSITIVE--NEGATIVE SPACE / FIGURE-GROUND RELATIONSHIP
PROXIMITY AND SIMILARITY