Hi shlomi laszlo 
I agree with Kodiak3D on the lighting,
There are a few other things to consider when you’re creating a landscape piece like this.
To create a sense of Depth, and perspective,. you can use several terrains,. move some away from the camera, and scale them up to create distant mountains,. a Middle ground,. and a Foreground,.. where your figures can be placed to give the whole scene a sense of scale.
Some of the shaders, such as the tree trunk shaders could use some different shades of brown with a fractal noise mixer, or gradient, and maybe some bump.
To me,. the main tree seems to be,.. kind of blocking the view,.
IF you imagine looking down a valley,. , you probably wouldn’t take that photo with a camera,.. with the tree in the main part of the photo, ..unless there’s something in the tree ..I’m missing 
You’d find a better position for the camera which gave you a better view of the forest, spreading into the distance.
It also looks like you have some Volumetric clouds in there,. but they’re way back behind the tree’s, and so they’re harder to notice and they’ll add a lot to the render time.
If you add a Realistic sky, there are several cloud layers you can enable and adjust, with different cloud types, and options..
you’ll also see an Atmosphere area where you can increase the Haze altitude and density,
this will also add to the sense of depth in the scene.
I hope that makes sense.
This is a scene I was playing about with, using the Genesis basic male and basic female, using M4, and V4 shaders.
The figure’s are on a little plane , with a terrain in the back,. and then duplicates of that same terrain, scaled, squashed and rotated to form different looking features.
Click thumbnail to see full-size image