If we have assistance, increasingly, it has to be willingly given (or subcontracted), and the willingness has to be properly defined with waivers and contracts.
We cannot --or should not-- snag or take an image of a famous person or character, and exploit it without permission for our own profit and fame.
Take broadly smiling Borat, for example. Or to be more precise, do not take Borat.
Edward H. Rosenthal, blogging for for Frankfurt Kurnit Klein + Selz PC discusses a variety of copyright-related claims brought by the actor Sacha Baron Cohen against a Massachusetts based Cannabis dispensary which used his image as the Borat character on a billboard, in total disregard for Mr. Cohen's rights, reputation, and feelings.
As Edward H. Rosenthal points out, "No matter how this one turns out, it is very risky to make commercial use of a celebrity's image...."
Most authors have blogs specifically for marketing/promoting our works.
David O. Klein of Klein Moynihan Turco LLP has some very good advice about using blogs and social media for marketing which is well worth reading.
Not many authors can afford to hire an influencer, but, if one does so, one must do it right.
And also three things to consider if hiring a model
Finally, from the UK, legal blogger Astrid Arnold representing Stevens & Bolton LLP shares a bit of good British news for someone who contributed mightily to the development of a movie, but did not get credit or a fair share of the writing royalties.
All the best,