Danilo - my crit was more aimed at you as an artist than this piece. However my advice of studying for a year would benefit this piece in the long run.
This is pretty much random image, there is no (fortunately for my nerves) a client.
In my job I often work for low cash and so must work fast.
So my point is do right image without thumbnails, blocking it out, and do a quick render smudging and adding few details on the storytelling targets.