I do not see
how will photo of your mobile game in hands of someone who looks nice help on promotion, unless it's about someone famous and handsome, but I doubt Gal Gadot or Margot Robbie will do this for $15
Because looks plays huge a role in advertising. As someone with some experience in marketing/advertising, I can tell you that if a brand/product/service, etc, wants to promote their stuff and they want a person (or a group) in the ads to market the product, the marketing campaign will preferably want attractive people (it's all about the perception and how, psychologically, beauty and attractiveness sells).
Since OP's product is a game, take a look at the Nintendo Switch commercials, sure the people in those CMs aren't Gal Gadot or Margot Robbie, but at least they're not hobos or someone you'd consider as extremely unnatractive which would turn people off. If the budget isn't massive, you don't have to be famous
and handsome in order to promote a product, handsome is more than enough.