The rivets look good up close. I was assuming there is some sort of blurred dirt or shadow layer around the rivets and panel lines that was making the lines of rivets stand out at distance.
As far as dirt goes, multi engined bombers often had a lot of oil staining around the nacelles and across the wings behind the engines. If you do paint these stains on they can look quite realistic if you also make them less shiny in the spec map. A top quarter screenshot with the reflections showing across the top of the wing but not off the stains works quite well.
BTW there are a few things I do when taking screenshots, particularly of NMF aircraft. First set the arena time to 09:00 or 15:00. With the sun lower in the sky it is easier to set up a shot showing reflections on the skin. Position your viewpoint at a 90 degree angle to the sun, i.e if the sun is east place your viewpoint to the north and you'll get good reflections off the shape. I try to get a shot where a single reflection runs across both the bare metal and less shiny painted areas as it really shows off the spec map effect. Also I hit the zoom key after going to external view and then zoom in or out, this gives less of a "fish eye" lens effect to the shot.
