Yeah the pixels are stretched too much. This was either scaled up or taken with like a cheap 3mp camera/webcam type deal.
It may look a little better scaled down but the only way to fix that is like taking a wacom tablet and digitally recreating. You cant really airbrush it unless you like redrew the lines and shit, it would be like a painting lol.
Here is an example:
Do a google image search for hyper realistic paintings.
That shits prob expensive though.
Check out this guys work, pretty nuts.
http://www.denispeterson.com/
Best of luck