>the image seems to be moresuccessful when there's more space in the direction the thing is>looking/going and less space behind.
About 25 years ago, I took a course in journalism. It was in this class that I learned the concept of "line of force." Simply, it means that in journalism photographers are taught to always pay attention to the direction of a person's eyes when taking people pictures. Always create more space in the direction a person is looking, which becomes the "line of force." This way you get the feeling that the person is looking into something, not nothing. Of course rules are made to be broken, again and again. One example... if you want to invoke the feeling of completion at a track and field event, like when a runner breaks the tape at the finish line, the bigger space should be in the back of the runner. Or when it is your intent to create a picture that is deliberately disturbing by leaving almost no space in front of a person and a lots of space in the back. This is a real attention getter.
Dan