I've been studying photos by famous photographer Henri Cartier-Bresson and find it interesting in many portrait photos he made he didn't fill the frame with the subject. Click here and you will view an example of what I'm talking about. He seemed to find something in the background that he wanted included with the photo. The photo of Adam here was an attempt to get the same composition as Henri would; the wine bottles being a target to include in the frame. I think composing portraits like this can make images more interesting. Not every shot needs to be like this though. Sometimes your subject needs to fill the frame. Especially if there is nothing interesting in the background.