Click the image as these forums have a nifty feature that images are zoomed in when clicked.
I made a quick but totally workable example of what I think might be more convincing for what I think you need. I went with a cel-shading sort of shading, and a cool-colored light source from above. I also avoided the use of highlights as it's not something you really see in rougher textures like that of a trenchcoat.
I don't think I am a shading expert but as far as I've understood shading, it has more to do with how shading works than how a particular object is shaded. I find that to really understand shading, you gotta see how it works in real life - how light sources cast shadows and how it can change colors of an object, bunch of other details as well.
You could also just look at a picture of a tenchcoat (with great lighting) and see how it's shaded to help make sure your shading is solid. Be mindful of lightsources though.
Also, never save as a JPG.... or did the image host turn your image into a jpg?
Saving pixel art in that file format is like stuffing the essay you did for homework into your pants pocket.