In order to run the Encounter at blackwall Keep with MapTool (praise it!), I tried to draw a photoshop map with 60 pixels as grid size.

The encounter takes place around a tower keep. Here is an part of the scenario description:
The keep itself is built out of black stone and consists of a single ground floor with a tower. The entire ground floor is buried under a false hill, and all that is visible is the tower itself: The door to the keep (visible only from the south side) looks like it has been broken open and hastily repaired. On the level above the door a five-foot balcony extends outward, giving the defenders a good vantage point and making it harder for invaders to enter the tower by climbing the walls.
Large sharpened wooden stakes jut out of the hillside, pointing away from the keep (toward any potential attackers).
And now my map, :

It is based on the scenario map that I extended. The upper floors will be added as stamps in MapTool and are not in this "ground floor" map.

My concern is mainly the land away from the keep which I feel seems too much "stamped" (I mean as if a stamp was ued to add the vegetation).
What should I do to improve this?