I started a thread with the same title over at DAZ and it seems to have hit a wall on what people can help with.  I'm trying to achieve the same realism as I got in "The Breakfast Nook" that is in my gallery.  Populus very kindly sent me a simplified version of his Peaceful Corner as a learning tool.  I've reproduced it at a medium scale and I'm happy with the lighting.  My problem is the apparent texture on the walls. 

Here's my shader that is on all the walls and the ceiling.

Here's my latest image.  I'm trying to figure out where the apparent texture on the walls is coming from!