Hmmm ... it's a very interesting question. One possibility might be to research what is considered a "beautiful" face. THe more you sway away from that, the less people are likely to like the character. As for a likeable face for a young boy ... how young? Things I think of that would portray "likeable" are wide, childlike eyes, smiling face, that "boy next door" look. It can also be mannerisms as well ... "likeable" people look you in the eye. "Shifty" people avoid looking you in the eye. "Bratty" ... pouty or frowned mouth, "I'm better than you" mannerisms, brows always scrunched in a frown. "Brainy" ... glasses, of course; sort of that "Harry Potter" look. 8-) Untrustworthy ... definitely shifty eyes and thin mouth. I almost wonder if there are cartooning books that might lend some info?