I made some changes to your sprite, I got rid of some colors and added some new ones. I added a light source which is located to the right of the old man.

It was hard to tell what that thing was near the top of his shirt, and I'm not talking about the pocket protector, so I threw that out and made it a more regular shirt. Now I also changed the pants and shown highlights to where they should be. I got rid of the red near the bottom of the shoes and changed the shoes up a bit. Something your piece is missing is AA (Anti-Aliasing) which I think you should look up some tutorials on that.

Your colors for the skin were a bit funny, some of them were merging with others, making it hard to tell the difference from another. One last thing, make sure you keep your sprites more interesting. This one that you made is not very interesting, I added some wrinkles in the shirt and the pants, I also put some highlights showing thighs and kneecaps.

Hope this helps!