Hey T3G, this is looking great. Good definition you threw into his legs. If you have a look at the two reference images posted, preferably this one:
You'll notice that their ass tends to be higher off the ground than their heads when they're standing. And that their mid back has a dip in it leading back up to his neck, then head.** Other than that, this is the only thing I can seem to see.
**This could already be done, as your model has his head posed down. Hard to tell.