Kabanellas wrote:couldn't thought of any

Well, perhaps dividing the map in several sectors. You could just divide the map in four "squares" - northwest, northeast, southwest, southeast. Then you could name the territories NW1, NE4, SW9, SE5 and so on... this is just an idea, and there are probably even better ways, but even this would be better than naming them all N1...Nxx, IMHO.
Also I assume the territories around the castles will be named by the castle letter and the number? I think it would be easier to players if you have the whole territory name written in the territory. Like, around castle C you would put C1, C2, C3...