here is a quick side view with sketched in arms. Notice how the helmet is rounded off pretty well.
Here is part 2. I continue to round off the helmet. I also work the chest and back inward.
Remember that the shoulder pads will stick out a bit beyond the sides of the helmet. Leave the facemask area pretty much alone at this point. Keep redrawing in your centerlines so you can keep the carving symetrical.
Next I draw in the arms. I have them hang a little lower than normal to give our player more of a comical appearance. You can make his arms thicker or thinner to make him as muscular as you want.
(In Tom's case I'd make his fella's arms pretty big to make the tattoo look right. I did make a Hines Ward for a friend. The tattoo did turn out pretty cool).
I work the arms in from all directions and make sure there is enough meat at the bottom to make the hands.