Outline is really jaggy, needs cleaning up. Some areas are one pixel thick, others are two pixels thick, and in other areas he just has random pixels jutting out. I’d also advise going easy on the dithering, it’s really a technique that should be used in moderation, and only when it’s really necessary. The anatomy needs work as well. The arms are too short, I think the arm on the right could barely reach his waist (and I’ll bet he’d really have to struggle to pat himself on the head). The shape of the head doesn’t indicate a solid knowledge of the skull’s structure, it should be less of an oval (not as pointed on top), and perhaps have a jaw as well. The neck is much too small to support the head. The feet look like we’re seeing them from above, whereas we seem to be looking directly at the rest of the body. There should be more lines on the basketball, and the alien hands confuse me as well.

The best remedy is to use references, always for everything. Study photographs of actual human anatomy, and try to replicate what you see, rather than resorting to simplifying the forms to basic symbols. Remember that we have WIP forum for improving artwork through feedback from other members.