Here are the six wall features mentioned in the structure roll post. you may find them useful design elements even if you aren't using random rolls. The images are based on a d6 landing in the upper part of the left side of the Walls (Doors and Exits) region.
Collapsed or Crumbling Wall: A section of wall has fallen over, cutting off the corner in this position. This works great for ancient delves; for a cleaner look, you may want to re-define this as Clipped Corner instead, causing one part of a wall to jut into the room and reduce floor space.
Excavated or Extended Wall: A section of wall is missing, connecting the main room to a smaller area. This may be rough, as in the illustration, suggesting that the room was altered years after its construction; or, it may be smooth, allowing L-shaped or T-shaped rooms.
Jagged Wall: A section of wall is either broken or not constructed along a straight line. This can produce minor alterations in room size or even provide crude niches or alcoves, which can be used as concealment for secret doors or hidden enemies.
Fall-Off: A section of the wall is missing, leading to another area with a lower floor than the main room. This is much like an Excavated or Extended Room modification, but with an added hazard, especially for those trying to move in total darkness. Tricky dungeon designers can include an exit in the lower area that leads back under the main room.
Ledge: The inverse of a fall-off: the lower part of the wall juts into the room, forming a higher level than the main floor. this can act as a vantage point for an ambush; or, if the ledge is sufficiently high, a nice place to put treasure in plain view but out of reach. The ledge may have its own exit on a higher level.
Slanted Wall: This end of the wall extends further out than the opposite end of the wall. If a Slant is indicated in the middle of the wall, this indicates an "A" or "V"-shape; if one or both of the corners opposite this wall are also Slanted, you have the option of interpreting this as a triangular room.