The problem with using celebrity PBs is that celebrities are, well, pretty. You're not going to find an ugly character because there aren't really any 'ugly' celebrities out there. You're in a tough spot to find an overweight or pudgy character because plus-size models are still made up to be pretty and aren't really that 'plus size' to begin with, and you're not going to find people who look like folks you meet on the street. Wrinkles on 40-year-old women are nonexistent, pot bellies on middle aged men don't exist, and the dorky girl who wears glasses and doesn't do her makeup is secretly cute because you'll never find a PB that matches the actual description.
That is all.
For now.