First of all, this shows some of your better color choices. The problem is that it's too dark, especially with the black background.

In Photoshop try adjusting the levels to 0 1.85 255. The hair and the gold parts of the uniform won't look as saturated, but you really don't want to go overboard with saturated colors here-it just overemphasizes what is too dark. You can then use the art history brush to gradually darken her lower half and the further parts of the cape. You'll add a bit of dimension by doing this.

If you want to add even more oompf, add some sort of backlighting to her, even something subtle can add an extra dimension. A mid to light blue is always a good default, or any kind of cool colour, but even warm colors can work here as well--just enough to add that something extra.

The eyes--you've got enough room, add a white catchlight to her irises. Again, it'll add a bit of extra life to her face, AND works best when white or nearly white.

Also, I take it you're the one that made the background black? You've got a bit of haloing around the lineart where the lineart has aliased. Either remove that haloing--it is a bit distracting--or make it pronounced by using a stroke. Also, I'd show the signatures--they're still there, they're just barley there--make them white or a color from the image and let them be seen! The missing names makes the artwork appear more generic to me.

Try these tips and see what kind of difference it makes.