I think it has potential, but you're getting too monochromatic imo.
I would start out by changing the windowbg2 class to something different - flat w/no gradient if it were me. Maybe a lighter blue, or if you're looking for something different, a brown or orange. Just depends what kind of look you're going for.
I would also do something with the catbg class. Depends if you want to keep it rounded or just plain squares or something different altogether, again it depends on you.
If it were me, though, I would stick with the "flat" look that you've got so far and stay away from gradients.
That's what I would start out with anyway.