Mike, this is a great start
Before I begin let me tell you I am not a very good teacher but I will try my best to explain,
For the background or for the facial features of the subject it depends on you ,what is required and what is not.
When you open the image in gimp take the rectangle tool and crop the portion to what you think is required,after that the filter step, artistic- photocopy,when you are in the photo copy mode the image will open with four sliders, mask radius, sharpness , percent black and white.
sharpness- pushed to the right full and the other sliders are ready to play with, depending upon how much detail is required for it to match the original you will have to move the mask radius slider(till you think it is okay). I am sure to some extent you are doing what I have written.
Next step is enlarge the image to 200, 300% you will see that the details are there and cluttered ,clean up what you do not want and at times you have to add a few lines to get the right image- each person has his own way of doing things and I am sure as you practice you will be there.
English not being my first language you will have to excuse ,overlook the fashion this is written in and I sincerely hope that my explanation has helped, above all and it makes sense
Thanks
Mahendra- I am taking a shot at Ben's photo.