The round black stroke, I left it because i thought it would help explaining the form.
I guess it's an interpretational option.
Thanks for the tip Gratheo, I'll keep that in mind in the next works

For fourteen colors, it's very nice. A word of advice? Try and avoid using pure blacks or whites. Shift them slightly - it gives the picture a little more depth.   

There a round black part at the very top, I'm guessing you wanted to remove it all. Otherwise this looks nice.