What’s wrong with this picture? Now there’s a dangerous open invitation for criticism! 

The mistake I want to draw your attention to is my left arm (highlighted in the second photograph).  My left hand is placed in my hair which is a good thing; my hand has something to do and is not idle or awkward. However my elbow is pointing towards the camera giving this arm a shortened, cut off appearance. Also the placement makes the left upper arm closer to camera so more emphasis is placed on this arm and it looks disproportionately large. 

The fix is simple. If I turn my upper body a little to the left, the viewer would be able to see the length of the left forearm as well as the upper arm and it would no longer appear shortened. The left arm would be further from camera making the arm look more proportional in size. 

Simple changes - big difference. 

For more tips on posing have a little look at my posing videos here.