The landscape is quite poor: Almost all of the map is covered with grass. Not even the different types of grass were used to make it a bit more realistic and detailed.
Then there are a few small spots of elevation. Here you recognizably worked with small brush sizes and tried to avoid big square-shapes - that's the right way!
Though, there's still a lot of potential to improve. E.g. at a place with stone, for placing a quarry, one can also place some rocks in various sizes, some ruined walls or towers, or some ruin-buildings to make it look more detailed and natural.
Another example where you can improve: The borders between sand/dry earth and grass are no straight lines! 1. They are not straight but curvy. 2. The grass doesn't stop immediately, but thins out and "slowly" gets less and less until only dry earth remains.
But overally I wonder a bit - castle builder maps usually are thought to give a surrounding to the player where he can build up a castle from scratch, without any disturbance of enemies. Here two thirds of the map are already covered with the player's structures. ;) If there is a big prebuilt castle already (and also if there is no castle), there should be a small story included.
Btw is there a signpost on the map? (If not, invasions and many events that can be called with F1 don't work.)
Btw: By looking carefully at minimaps and ingame details of maps, one can learn quite many.
Just look at some maps of "surajsubba", "sulis", "qtlilkeg", "Warlord_Designs", "AZ ViTrAzhAs", "the Dragonheart", "TwoDie" or "Lord_of_Hell" for example. These mapmakers made some really great maps!