Better but dont forget the rest  .

it's just not how we shade a ball , I did a little edit for you , it will introduce you to ambient lightning , and help you get a more realistic look :



so first dont forget to outline your ball with the darkest color and AA your ball with the background and the inside , and also dont just throw colos like that use some dithering between to enchance the realistic look . and dont forget the shadows follow the curves of the ball , the ball is not flat .
as for ambient lightning i hope this will help :


Okay i dont have much time to fully explain it but if you have any question go ahead ,
hope i helped  .

In fact my idea was a front light source completely different from the moon light source , it was okay for me but it seems it doesnt work.
Also the arm is supposed to behind the body like this :



It's a shading effect but i must confess it's not too obvious  .
Thanks for the advices 

Hum i think your tiles suffers a lack of details , i made this in a rush for you , it's not good either but it may illustrate what i mean.



as you see i didnt just randomely pixeled like you did but i tried to get some forms out there
i also did a second one slightly different just for the diversity.



Now if i try to tile it it would'nt look as "Tiled" as yours :


I hope i helped you with these and if you have any question just ask   .