I think this sunflower picture is missing something. IMHO it looks like a snapshot. Try making the photo yours, how do you see the flower differently then the 20million other photographers? Take artistic liberty with your pictures. You have a digital so you don't have to worry about wasting film. Take 80 pictures of the same sunflower, but make each one as different as possible. Change the aperature, shutter speed, shake the camera on purpose, shoot against a black background or a red background, shoot in black and white, shoot with the white balance set to incandesent lights, shoot in wide angle, shoot macro, shoot with fill flash & shoot with no flash. I love to shoot sunflowers, check out my portfolio, if you get the chance. I'm always trying to think of different variations to the shot.
Sunflowers are awesome, and since your neighbour has an abundance I think you should go back and explore them some more! To me, this one seems a little soft in the middle of the flower... the leaves seem really sharp, but the flower itself is not. Could be the scan. Like the yellow against green.. it really makes this stand out!