They're a good idea. Diversity is important, not for pr, but since it let's people who don't want to set a custom skin have a look they identify at least somewhat with (though the skins are pretty generic still and most people won't identify fully with any of them of course). Also, as someone else said, it's easier to tell people apart. This is better than the weird middle ground that was having a male and female skin, but nothing else. Either go with one skin to represent them all or go with more diversity, though the latter is better of course.