I like NPR renders that use painted on textures like in this project by Gregory Khodyrev (preview below)
The only issue is that the shadows are normally painted on as well so they aren't very animation friendly. I was thinking what if you could have two layers one lit layer and one shadow layer. Place the shadow layer onto the material and use some type of variable like a normal vector or a sky texture as a movable mask using the lit layer which can simulate sunlight hitting it. Or alternatively use a shadeless material, set up a variable that detects weather or not a normal is being hit by a ray of light, and if it is it will project the lit texture onto that normal.
However, I don't know enough about about the node editor to know if either of these methods is even possible.