Haha, he's dressed as a bear? Cute
Constructive criticism you'd like? Not sure really... never received any myself. Only advice I can offer to aspiring artists is to never stop looking at other works and never stop experimenting. Judging by your photo in the 'cartoon me' thread, you're still quite young, so I'd say from what I see here you have a wealth of potential with a lot of time to develop it. I'm 23 years old and the stuff I do has been honed by a life spent in a darkened room hunched over a sketch book spurning all social interaction... not to be recommended.
But the good thing about art is that it's not qualifiable or quantifiable. What you do is what you do, and it's always gonna be good.
Have some fun playing around with shadows, that's an idea. Pick an angle for the light to be coming from and then do shading along the opposite edge of the figures and objects. You can take some cure by what you see around you in the real world - for eg: shine a torch on your arm and take note of how the light/shadow falls.