Very nice design - I hope you don't mind a couple of suggestions:
Try the map with the saturation of the colours toned down to about half what they are now.
You could make the castle walls more interesting, by putting in slit windows, buttresses and columns etc.
There is useful reference material on the site
here: reference material
here: stunning castle plans - all done in Microsoft paint!!
It's worth having a root around the reference material bit of the site, there's quite a bit on castles there.