I agree that you don't see many accurate representations of heroes that have single-digit charisma scores. For my part, I try to stay true to the stats.
I have an arrogant, absolutely ordinary elf wizard (cha 9), A friendly, curious, slightly overweight / potbellied diviner (cha 12), a weird, taciturn, pale-faced, formol-reeking gnomish necromancer (cha 7), an angry, unkempt, dirty, patch-eyed, vermin-ridden dwarven barbarian (cha 6), etc.
On the other hand, if a player describes his 10-charisma character as "Alyssa Milano, only better"*, then there should be some moral trait that's absolutely horrendous about her, and that's why even if people find her incredibly hot, they think she's a total b*tch (stereotype if there ever was one).
AR
*As if!