Pick up two books:

Understanding Comics by Scott McCloud

and

How To Draw Comics The Marvel Way by Stan Lee and John Buscema.  These two books will cover understaning not just how to make your panles/poses more interesting but also why certain things work while others don't. 

I also discovered that some poses require additional elements to sell them. For example, the punch you posted. Despite the fact that the shoulder is raised when it should be lowered, the punch itself is decent but lacking something. Simply put, that something is a reaction. There's no villain being thrown back from the punch and that can take away from the impact of the panel. I learned this lesson while sculpting for a challenge. Some poses require both the action and reaction in order to work.