People will be that you could help me finish this, or even have ideas?

Let's see.

Right now, there's not much going on in this piece. The wolf is just standing still, staring right into space. To make things more interesting, I would change the wolf's posture. Howling at the moon is cool, but perhaps cliché. Perhaps the wolf could be moving into the river or coming out of the river, or even just looking at its own reflection or drinking from the river.

Beyond that...

- I agree that everything is too bright.
- The light source of the mountains seems to be directly to the left, instead of top left.
- It's a bit strange to have the stars outshine the moon.
- The wolf's anatomy needs a lot of work, so you should look up some reference pictures. Also, why is it brown? Most wolves are grey, although some are black.
- The flat line by the foot of the mountains seems to be some kind of horizon. The river goes higher up than that, almost like it's on top of the grass and mountain, instead of below.
- The grass looks very flat, it should slope down to the river. Rivers tend to be the lowest point of any scenery.

Finally, I'm not wizard when it comes to composition, but I'm getting the feeling that this is not ideal. It reminds me of my own work, and I think the problem is that there's no natural focus in this piece. It's almost like the picture is divided into four equally big sections, because you wanted there to be a wolf, a river, a moon and some mountains.
Check this out.
http://en.wikipedia.org/wiki/Rule_of_thirds