I tried changing the style of the character, by caricaturing him a bit....stretching the likeness of the top three actors, I'd like to see as Robert Neville; these were, Ben Stiller, James Stewart and Jason Segel.
I also did a few thumbnails, testing to see what clothes he might wear...I put the clothing thumbnails adjacent to the heads that fit the body type. so Jason Segel heads are from A-C and 1-4 are his clothing thumbnails
In terms of style, I like the cell shaded tone of games like Borderlands and the Walking Dead tell tale game. The short animation Black Water Gospel , made me want to have this very cartoonish feel in terms of design but realistic in terms of the tone, at the end of the day Robert Neville is the last of the human race, it's actually quite a depressing story which pretty much describes the end of civilization as we know it and a birth of these Vampire like creatures.