Try adjusting the levels or curves, depending on what options you have available in your image editor. I usually tweak a render in Photoshop a little bit to get a sharp punchy pic.
Is the black material supposed to be a soft grip rubber? The reason I ask is a lot of the great contours you have there are lacking definition because of the lack of specular. Maybe try to apply some noise in your bump channel that is really small scale and intensity. Then increase your highlight value slightly(20-30) and reduce your shininess value(2-5) that should let you pick up some edge highlighting but still make it look like soft rubber.
