How many lights are you using? What intensity setting? I always have at least 4 in every render. The first three would be the "ambient" lighting -- set all as "infinite", no shadow, and place in the y0, y120 & y270 positions at x-15 at 25%-50%. The fourth light is my "sun" or spotlight, which is the only one that will cast shadows. I keep my sun on the infinite setting for 99% of my renders and move it around as necessary. By setting your first three lights at different intensities, you should be able to lighten up your image considerably. ALSO, don't be afraid to use the "highlights" button in the material room. Use a dark grey or deep blue color and slide the highlight bar to around 50% and you should bring out some detail in that uniform. Nice character face, btw.