Adobe Illustrator CS 2
I don't know how much this actually looks like the boy I based the picture on, but for me, it captures some of his thoughtfulness and complexity.
Just a straightforward illustration. I created all the base shapes, then used the Offset Path command with negative numbers to make smaller inner shapes. The base shapes I gave darker colors, the inner shapes lighter colors, then blended.
I used the Free Transform tool to put the sidewalk and text into perspective. :)