How would I go about editing a render of a 3D model to look more realistic?

Question

I have really got into the game, The Last of Us, and fancied doing some art, I have the software to do the rendering, but the output is not realistic in the slightest. At the moment I have been using GIMP, but software isn't the problem - so any software you feel comfortable answering with is fine.

I have 3 imaged to show:

1) What I Started With

2) What I'm Aiming For (just to get me started on track and so I know what I'm doing)

3) What I already have: http://wikisend.com/download/557596/image.xcf

Answer 1

If you can work in 3D, adding lighting to your scene and rendering with ambient occlusion will add a lot of depth. Try using lights that are not white and tint your flood and fill lights with cross compliment colors for a more dynamic feel.

If you are only working in Gimp, simply paint over the base layer of the character to add depth and mood. Start by replacing the green screen with at minimum an FPO image that has the tonality you want the final background to have.

Answer 2

You need to add some lighting to your image. It's very flat. Notice the shadows and highlights in picture you're aiming for. Yours doesn't have those.