Shutterstock has a clause expressly forbidding use of images containing models in this way (bold mine):
RESTRICTIONS ON USE OF VISUAL CONTENT
YOU MAY NOT:
Use Visual Content other than as expressly provided by the license you purchased with respect to such Visual Content.
<strong>Portray any person depicted in Visual Content (a "Model") in a way that a reasonable person would find offensive, including but not limited to depicting a Model: a) in connection with pornography, "adult videos", adult entertainment venues, escort services, dating services, or the like; b) in connection with the advertisement or promotion of tobacco products; c) as endorsing a political party, candidate, elected official, or opinion; d) as suffering from, or medicating for, a physical or mental ailment; or e) engaging in immoral or criminal activities.</strong>
<strong>Use any Visual Content in a pornographic, defamatory, or deceptive context, or in a manner that could be considered libelous, obscene, or illegal.</strong>