You could play with the whole face, the eyes for example, they are kinda stuck on a line, especially the eyebrows.
Manga/Anime is most of the time thought as an easy style, it's not to me.
Takes time to understand and stylize something and even if you succeed at drawing some poses well, as soon as you will have to draw from an other point of view it will be very hard.
I won't tell you to do traditional nude drawing and buy tons of books on the subject but you could look at your own face on a mirror or take pictures and trace lines to see how much the face elements are translating.
With this style and at this scale you have to exagerate at least a bit.
I don't want to sound like I'm patronizing you, anybody can have fun while drawing IMHO.
made a crude edit. Better than my crippled english
