Squared things are boring and I was thinking that a bit more diagonals would really help. The idea is that when you build two pieces of wall in diagonal that only touch by their vertex the game would display them as a 45º diagonal wall. Maybe it could have too a hitbox/collision in diagonal.
A further extension of this idea is to add too 60º walls.
I show several examples in the screenshots: https://db.tt/rFRtP6W0An
Cases 1, 2,3 and 4 should be 45º walls.
Case 5 should be 60º wall.
Also a tool to draw these walls would be very helpful since currently we can have to click once for each square.
I don't think the engine that Rimworld uses is capable of doing 45 degree angles. It's very limited, apparently we can't even do Z axis.