Again, I saw your comment request on
Generally, it's very interesting. The hair are nice, while they seem a little unatural to me. Try checing out this tutorial : www.deviantart.com/art/Abnorma…
Instead of only using red and black, you could've used purple, orange and brown. Check it out !
Also, something I noticed on your artwork in general : you should explore your program and discover everything it can offer you. The difference between photoshop and other programs such as PTS is that it has limitless options when it comes to adjustments and settings. Try using gradients, color balances, layer modes, changing saturation, brightness, hue, color balance etc. Small details like these can really transform an average artwork into a very interesting piece.
In the beginning, when I saw this and before realising it was Gaara, I wondered why there was so much black around his eyes. Then I realised there were dark rings. You should've used a harder brush to draw them, that way it would've been easier to understand what they are.
The nose and lips are perfect; no need to correct anything about them.
Now, your question was about the face looking less flat,correct? Well, this is all about shading. Try to use harder brushes, different shading colors -not only black and white. Remember that a soft brush is used for smoother gaps like cheeks and that harder ones for bigger angles, such as the nose, the neck etc. Also, remember that face expressions are caused by expression muscles (e.g. between the brows, like here), so they should be shaded too -with a harder and smaller brush, as the deformation is small in range, but intense. Finally, note that, when it comes to shading, the smoothness of the shadow depends on the distance between the two objects (the lighted one and the shaded one). So, in this case, the hair should drop a rougher (and lighter, btw) shadow on the forehead, as they almost touch each other.
I think that's all. Keep on training ! c: