I can understand people wanting to use Anime pictures, sometimes it's appropriate in certain settings. But for the most part, when I create games, I'll specify that either all real life pics need to be chosen, or all Anime. I [almost] never allow a mix, since in my opinion it subtracts from the overall picture in my head.
As for it being the decision of the perspective player's, and not the GM, who usually makes that choice, I can't really agree with that. I'm not being argumentative, but the power to make those choices are up to the GM. If they want character bio's to be formatted a certain way, have one specific style of picture or description, or even what ages each character should be, than it's their right to specify those things. If perspective players don't like it, than they need not join said game.