Pretty sure that I'll be one in a long line of people giving this advice but I feel I should explain my lower than average score.
On-camera flash = evil (a safe conclusion for 90% of the time). You will notice a harsh shadow behind your subject and a very 'flat' light on his face. The key to portraiture (I've not mastered it yet by any means, but I've been taught by many experienced photographers) is to have the key light, the primary light, at least 10 degrees off the axis of the camera. It gives depth to the face, makes the scene seem more 'real' to a viewer, and totally gets rid of the 'snapshot' look which flash photography unfortunately carries.
Positives: Kudos on not blowing out any of the highlights on the subject. Whether this was manually set or done by the camera, I am impressed at the even nature of the exposure. There are no glaring hot spots (apart from at the top, but I'm still not sure if that's just a color of paint on the wall).
Cute kid, but you're to close to the background, which causes harsh shadows and flash kickback from the wall. A 30 inch off camera umbrella would do wonders for this setup. If you don't have the off camera equipment, but you have a Bounce-Flash, bounce the light off the ceiling and light up the shadow areas with a white kicker-board placed just below the frame.
White foam-core board found at an art store is really cheap. You can even spray-paint one side silver or gold.
not bad, but the flash light is a bit harsh. some ambient light would have softened this nicely. de-greening his face and shirt might help a little too - they really are very green.