EAGLE: Change shape of Repour All Polygon
Anyway, the surface has some empty zone close to pad that I would like
  to fill with copper.


That may not be sensible because they are called thermal reliefs and allow the component to be properly soldered because the copper mass doesn't take too much heat away from the solder joint and therefore doesn't necessitate excessive heat given to the actual component.



You can always loop a regular copper connection across those "spare areas". Or just setup the thermal spokes to be bigger.