I do think you need to work on depth and proportions a little bit. The characters always seem a little flat, particularly in their torsos. The muscles appear to be drawn onto their shirts, if you understand what I mean. Also, shading would work wonders if the picture isn't to be coloured, make it look less 2D.
And as for the proportions, the hands always look tiny and the heads always look huge, but I'm sure you've cited Akira Toriyama is an influence in the past, and he does much the same.
Hell, what do I know though, I don't even have the attention span to finish a piece of art once I've started. Just trying to offer some constructive criticism.