I have wanted to build a castle for a while, but money is tight right now. I like the figure dioramas that you have built, you did a great job with the base and the figures.
I came across this website many years ago, the author of the blog is building the castle and village of Clervaux in 1/35 scale, even tough the setting is different the techniques he is using can be helpful. Basically he is using construction foam both blue and white for the base of the terrain and the walls of the diorama, then they are covered over with stone, wood or other building materials. From what I understand, a master brick wall pattern was made, then dupicates were created and glued onto the walls of the castle and surfaces. But his construction technique changes for the construction of the town, check out the site below to learn about how the village is being built.
Here is the website:
diorama-clervaux.comThe author is not as active on the model building forum Armorama any more, now that he has is own blog and portfolio site. the forum post still exist but many of the photos that are used to explain the concepts are long gone.
You can check out this post to get a idea on how the diorama was built.
Armorama forum postGood luck on your project and keep up the great work.