Ok, I'm going to point out where Lucas is deviating from standard proportions, it is up to you to determine if thats on purpose or not.

The thing about general proportions is this (at least what is usually taught in artistic anatomy): Usually the way we recognize a person from far away (across the street) is becuse of their unique characteristics, which deviate from the 'averge' that out eye is used to seeing. Standard proportions that you find in various textbooks is an attempt to descrive what majority people see in their head as comfortable proportions. When out brain sport something different, we go, oh, I know that person... because of how they deviate fron the bland middle human in our heads. They can be taller, shorter, long legs, short legs, wide body, narrow body and a myriad of other deviations. (deviation is not a bad thing here), itls just a professional term to define a difference. In scientific language there is a 'norm' and a deviation - that's where it came from.  

 

These are just some things I caould find in the time I have at the moment.

Screenshot 1 - http://gyazo.com/a481835f7d4d1a3b0da2069216cfbf9f

Top left - earhole to bottom of the nose - when looking at a face in a straight-on positon those line up horizintally because they are both sitting on a sphenoid bone which is one of the several bones in the base of the skull. If they donlt line up we can get a feeling that the character is looking dwon at us, buif that is not supported by the other planes of the head showing us a bit of the bottom, it may look like something is off or make the person look a bit longer faced then average. However, you have to account for a little bit of a nose cartilage and flesh to hang over that line. Tricky part about the head is that we are all so highly sensitized to facial recognition that 1/8th of an inch (life size) is a lot.

Top Right - Shopulder girdle assembly. There are a few bony landmarks on the shoulder that will define where the axis of rotation of the humerus needs to be. Arms (appendicular skeleton) are attached to the trunk of the body (axial skeleton) via shoulder girdle, which mostly hangs on clavicle, scapul, muscles tendons, chewing gum and piano wire.  Pay special attention to how Coracoid process and acromion process come together with the end of the clavicle to encompass the head of humerus. That will really narowly define where the axis of rotation of the arm needs to be. In Lucases' case it seems to be farther in from the norm, not just the axis of rotation but the bony landmarks too.

 

(ok, darn, I was going to do more byut my wednsday sketch sessions people are here half an hour early so I have to cut it short) I'll do more tomorrow or later.

Here's the rest of the screenshots, but I donlt have any pointers to go with that.

http://gyazo.com/a3bba9c7f416d526f373edb2bd811286

http://gyazo.com/a616ec65403b38e93138e228586cee62

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