All you really need to do is remove the white AA and this'll make it through the public queue...

 I think you should put the white background back in.  It's your piece, if you like it with the white background, use it!

I really like this but I agree that the kid's torso could use some more contrast!

 lolwut.

-Nice lighting on the monster's jacket/shirt.

-The kid's torso and arms could use some more contrast.

Very nice but head shading of monster doesn't fit light on monster's clothes.

Child, sword and staff need more detail to fit in the picture.

 Nice light effect :D

But the theme is abit random...

white backgrounds are usually pretty ugly and too bright too stare at, so it's usually best not to anti-alias your artwork to a background like that, especially if the background isn't helping the piece at all. Ideally the art should look good on any color background.

 {BR} Caso não tenha percebido a Joint não aceita pixelizações. er.

Without transparency is ugly because the background is dark gray.