This is not mine, but a simple fan rendition I saw, with the existing factions, could demonstrate the potential castle could have with kids with the proper marketing and also appeal to adults.
A larger image is available on my flikr...
Black Falcons: Lawful Neutral - Conservative mercenary kingdom, easily defended by mountain ranges and fortifications. Ruled by a citidel on the outcropping of land known as 'The Iron Fist'. Allows the free travel of merchants but unconcerned with the affairs of others unless there is a good profit involved.
Bull Knights: Chaotic Neutral - Barbarian men of the wild North East, loosely organised under a king. Enjoy a good raid, peace with them is fragile at best. Wild forests and mountains, rolling hills and a stoney coast line.
Crown Lands: Lawful Good - The largest Kingdom, I put the crownies in the centre (they represent the house of the King to me). The 3 Lion Knight factions have sworn fealty to them. There exists a certain degree of corruption within their political system and certain figures may not always have the peoples interests at heart... The kingdom boasts the most fertile lands in the realm and is a mixture of mountains, lakes, woods, pleasant countryside and riverlands.
Dragon Knights: Chaotic Good - Free folk that live in the cold north, excellent warriors but unable to compete with the political schemings of the Royal Kingdoms. Geography is a mixture of Mountains, pine forests, rivers and farmland to the south (Skyrim anyone?)
Dragon Masters: Neutral Lawful/Order - A sort of mercantile and arcane faction, I'm currently building a medieval MOC with an Eastern/exotic feel and they make great city guards with their elaborate helmets and mustaches aplenty. So they've been given a desert kingdom.
Dwarves: Neutral Good - The dwarven kingdom lies in a heart of a mountain range where they are able to explore underground without too much trouble from the surface world. Enjoy trade with most non-evil factions.
Elves: True Neutral - Occupy a large region of woodland inbetween the Lion and Dragon Knight kingdoms. Enjoy good relations with the Dragon Knights as they are viewed as less industrialised and closer to nature than the Crown Kingdoms.
Forestmen: Chaotic Good, made up of exiles and opponents of the Monarchy who fight injustice and corruption. Based in the Kings Woods to the west of the Capital.
Orcs: Chatic Evil, a loose confederation of tribes that occupte the Horde Lands to the North East.
Undead: Neutral Evil, A dead city on the edge of a great salt lake. Rulers tolerate a couple of slaver/piracy ports to the north in return for heavy tribute.
Vampire Bat faction: Lawful Evil : A land of mostly black volcanic desert and mountains, ruled from a Dark Citidel atop a solitary peak on the peninsular. Includes the Spider Jungle to the south and a mercantile port ruled by Dark Mages.
Vikings: Chaotic Neutral, launch raids over the entire west coast of the mainland from their ports on the Dagger Isles.