well as a suggestion i can give is that when u will incorporate more than one person(monster) in a picture you must keep ther bodies somehow anligned. In this case the boy is like tripping backwards but his expression is not like that,thus there is something wrong about its perspective. i think that af he is rotated a bit closer to the girl and arrange the features of his face in that condition, everything would become just fine:) Apart from this observation, the rendering looks fine for me do u use copic markers?

The perspective on the kid in back seem a little skewed. It's a sweet image, though. Very calm and happy.