Anything can serve as a 'type'. Just about any physical or personality trait, or even something they're good at. So a person's type can be something as simple as 'funny', or something like 'brooding musician with dirt blond hair, an old car and a collection of worn and torn up jeans'. Or you can slot people into stereotypes and go with 'jock', 'nerd' and so on. That's sort of dated where I come from, though.