As fashion changes, getting bolder and more exciting every season, so too do the faces behind the biggest brands. Whether their muses are walking the runway or the red carpet, designers are clamoring after a new, more diverse set of faces with an impressive following of their own to model their clothes. From established trendsetters like Rihanna to fashion newcomers like Riley Montana, you can spot these jet-setting "It" girls working with fashion's biggest designers -- be it strutting the catwalk or sitting front row.