Thanks for you comments guys, I am quite motivated to improve the technique. For me the most important was to have a quite clear map, as well as not making a map too "real" so I think that I achieved it.

Since I think that a map can be quite improved depending on the time you spend on it, I think, this didn't take too long, so I'm happy with that as well.

Now I am very interested in mountains and this half grey layer you mentioned, could you please link me to this tutorial?.