There are many factors that lead to a design getting rejected. When it comes to characters you need to think about how you are going to actually use them. What does the story need? Are they going to be in lots of ‘action poses’? If you’re not sure if they can then try drawing them in various poses. I really like having the arms really low on the body, but I think I might need to give him another round with longer legs. That way the arms won’t get in the way when he’s walking or running.