I am curious on this if your light source was closer it would have broght more definition to your specular highlight on the cue ball and imho would ave givin more attention to the cue ball. Also if the white balance on this was a little better the cue ball could have been whiter. Notice how some of the balls in the back ground have shadows going from left to right?? I think it would be cool if all the shadows from the balls could "point" to the back of the cue ball and/or make some sore of interesting pattern that draws additional attention to the cue ball.
Good interpretation of the challenge. I like the detail in the cue ball's wear marks and the isolation you've created, however, a different POV and possibly more variety in placement of the background balls might have made the overall composition more interesting imho.