If you want a richer look, you could try a levels adjustment layer over the top of everything. Just move the center control (gamma) until you see something you like. Adjustment layers will essentially apply an image adjustment to everything beneath them, but they're completely nondestructive—you can tweak it or turn it off at any time.

Regarding that top area, just throw a label on it that says "Terra Incognita" and it's no longer a mistake!