I hate to split hairs, the tileset is already quite amazing. Nevertheless
1. I think you should be able to make wider gates, the current arch can only be 2 or 3 tiles wide, that's a bit small if you're making a big castle with these tiles.
2. A connection piece that connects a straight wall with a round tower would be helpful. (see image) I realise that the problem can be easily avoided by building differently, nevertheless, I think a connection there could give the tileset a lot more potential.
Also, what is the wooden thing that goes on the wall? It's a bit hard to make out.