Hey mertgenccinar thats a very nice picture. Here are some things I came to think of. I made a little paintover.
-Area of interest. Think of where your area of interest are. It’s his face right? Keep the highest contrast there. Right now in your pic we only see the big window in the background and then the brightly burning goggles. The figure itself gets lost. I would suggest darkening those big bright areas and work up contrast on the face.
-Pure black on skin is a big no-no. Look at the shadows on the sides of his face, mix in a color, any color. And living skin always has color variations in it. For instance the ears and nose tend to look more reddish and chin and cheeks on males are often a bit bluish.
- Render the form. The way you have only rim light on the back of the chair and shoulder makes it look a bit flat, like it’s made of paper. The light is clearly coming from above so it would lighten all upwards turning surfaces like the top of the shoulder.
Entertain the viewer. Big straight lines are a bit boring. Break them up, ad details and texture and give us more things to look at. His goggles are a bit too ordinary at the moment I think.
- Color circulation. When you introduce a new color like in the yellow in the goggles it’s always nice to have the same color echo somewhere else in the composition. It can be anywhere and just a tad. But it tends to make things harmonize and look more unified.
-work form big to small. Don’t get bogged down in small details before you have got the big shapes totally worked out. Stay zoomed way out and work with twice as big brush size as you feel comfortable with now.
-Storytelling. Very important. That’s what makes us drawn to a picture. Why is the guy so sad? Is he being kept prisoner and made to work on a devastating super weapon for an evil villain? Most likely not but that was my thoughts while doing my paintover. I am sure you have a much better idea for your painting. But always think of the story and give the viewer some hints about what’s going on. What are those big lights outside the window?
Once again beautiful paining and keep rocking!