This glorious castle oversee's all of natures magnificent beauty. This castle is protected by an enormous mote which stretches from one side of the castle to the other. Death traps are set up outside of the walls so that no opposing troops will have access to teh castle. The few ways to get in are the Gates which are equipped with drawbridges. To the east of the castle lays the much needed resources along with natural waterfalls which gives you a surreal feeling. The castle itself is very confusing to navigate as an enemy. The stronghold is placed at the very top where it is protected by the inpenitrable walls and death traps. Enjoy!
Maybe you should try and make a magnificent map with wide open spaces and mountains without slopes at some places so you can build your castle against them for overwhelming defence. Not implanting a castle in your map would also be cool becouse then the players can decide how and where they want to create their castle, if you still want a castle in, put alot of eyecandy on it. a signpost also is a must in a freebuild...else you won't be able to test your "castle" against enemies.
Well that were some suggestions for a map(you'll probably know most of them)