He used my ink brush to add details.
Here are some inspirations for you, pictures from the Chateau de Chillon.
Look at the sundial on the side of this building. Do you see those curved supports under the roof? These projections are called machiolations. Defenders could drop missiles on attackers from there.
We think of castles as being made of exposed stone, like this, but
this castle had stucco spread over the stones, as shown in the picture above.
This wooden gallery on top of a wall is the allure. It is fun to walk in an allure and look down into the courtyards on each side. Inner courtyards are called baileys, or wards.