Hopefully the scars are visible enough.
First row: Default female Shepard, level 5 scars (Full renegade scars), no glowing eyes.
Second row: Default female Shepard, level 5 scars, glowing eyes.
Third row: Default male Shepard, level 3 scars (the scars you start off with, as far as I know), no glowing eyes.
Fourth row: Default male Shepard, level 5 scars, glowing eyes.
There is, indeed, a difference between the scars that I wasn't aware of; hence why I decided to do the third row as level 3. Female Shepard doesn't seem to have as much scaring in the later stages.
Mass Effect 2, Shepard(s) © BioWare/EA.
You are free to use this reference however you wish. You can also download the full size version which is better quality.