I recently watched an interview where director Guillermo Del Toro talked about the time and effort he puts into the design and look of each of his movies. He said that every detail has a purpose and a meaning. He referred to the details as "eye protein, not eye candy".
I thought that was excellent. Because that's exactly the way I approach the detail I put into my own art. I put a lot of time and effort to designing the smallest of details in each portrait. Every detail has a meaning and it symbolises something about the subject of the portrait. For me, the details in the portraits is what bring them to life.