Regarding light, you need something dark to show how much something else is bright.
Best way to bring light and illumination is to put it next to something very dark. Like flashlight in completely dark room.
In your fairy sprite all colors (inside outlines) are so bright and bland that you can even separate them at first glance.
You need to add more contrast to it and if you want some bright and cheerful don't use dark outlines.
Here's the small edit. Maybe not best dark-light example but cute.
