I was struck the other morning by this combination of shadows and geometric patterns on a wall.  It seemed the perfect indulgence for an IPhone image, converted to pure greyscale, and I felt, in the end, that it was better without any toning.  I had zoomed in just a bit when I took the image.  As a result, I found that any amount of sharpening accentuated the pixels unpleasantly.  So in the end I did some cropping on the final image and a little dodging to light zones in the shadow regions and and complementary burning in to shadows in the light areas.  I like the end result and I am almost always amazed at what the IPhone 4s camera can accomplish.