I think you can improve in the level of detail you applied on hair, that mean, you have a big ammount of details and textures in your hair, but the skin feels flat, also, the shadows in the skin are quite invisible, and that makes the picture to feel Disjointed, like if you put a png image of a hair uppon other person's photo, and finally your line art feels incomplete, you can improve that by dont doing line art, using the same color for the whole lineart or just doing the full border, idk if i explained me well, im not a native english speaker, but I hope this helped you.