This is fantastic, I'm a grown man and have loved Lego Castles for 30 years. I enjoyed looking at the pictures so much! It is very hard to find all the good pieces to make this so special though. If anyone has a good suggestion for finding all the specialty pieces that would be great. I picked up the medieval village recently, those houses would look nice around the castle.
Try to build up the landscape around it, add some hills brickbuilt trees, and maybe a few village homes. Also, work on the rockwork around the castle. Make it less square.