For better brightness, just increase the saturation on a select color or two -- you will find that the more prominently used a color is to emphasize other forms or details (such as shadows), increasing its saturation will help brighten your overall sprite without every color appearing too saturated.
That being said, I'm having trouble understanding the area under her neck and around her chest/shoulders due to that color HDMD mentioned.
Is it a shadow? Is it a necklace chain? Whatever it is, I would suggest either doing away with it and leaving it bare-skin there, or tweaking the shoulder outlines down a little so that her neck appears longer and that we can understand it's a shadow of the neck/chin area if that's indeed what it is. Atm, it kind of reads like a necklace or brooch of some kind, which is just too much detail for one cramped area on the sprite. Not to mention it's difficult to see the difference in its color from the 'jewel' unless I'm zoomed in 500% to begin with.
Just food for thought.
