Proper Posture on a flat bar road bike
If it's not broken, don't fix it. The act of folding ourselves onto a bicycle, (especially one with any kind of aerodynamic advantage over a mountain bike) is not a natural-looking position for a human body. We're built to be more or less upright, which is not an aerodynamic position on the bike.

So, if you're comfortable on your bike and feel like you're ok with the amount of wind-resistance you create for yourself, and your bike is properly sized for you, there's not much you'd really want to change.

A couple of general bike position loose guidelines (yes, general and loose are a bit redundant here, but these are not hard fast rules):


If you look down at your front hub while riding, you want it to be somewhere in the vicinity of being hidden by your handlebar.
For a commuter bike, you want to be able to look forward (with your head more or less erect) without feeling like you're craning your neck.
In said upright-head position, you shouldn't have to stretch for your handlebar.
Your seat should be at a height such that your leg is mostly extended at the bottom of the pedal stroke, but you should not have to rock your hips at all during the bottom of the pedal stroke.
Your seat should be situated fore/aft such that you can do the following:
a. Tie a weight on the end of a string.
b. Hold the non-weighted end of the string in the slight hollow on the outside front of 
 your knee.
c. The string should fall close to the spindle of your pedal when that pedal is at the 
 front of the stroke (3 or 9 o'clock, depending on how you look at it)


If all these things hold more or less true, and you're comfortable when you ride, don't stress what you look like.