A signed client cannot hand you permission to use their face
In this town a name and a likeness are licensed assets, and the person they belong to is rarely the only one who has to agree.
Nashville runs on rights. An artist's name, image and voice sit inside contracts with a label, a publisher and a manager, and approving commercial use of them is somebody's actual job. A client can be delighted with your work and still have no authority to appear in an advertisement for a law firm.
The same logic reaches further down the industry than people expect. Session players, writers, road crew and producers sign agreements about what they may say publicly about their work, and a photograph taken in your conference room can breach one without anybody intending it.
So treat every face other than your own as a permission problem rather than a favor. Written agreement from the person is where it starts and not where it ends, and in a market this size the safe answer is to publish nothing that identifies a client at all.
Confidentiality points the same way. The professional and creative world here is small enough that an anonymized story gets matched to a name by somebody who thinks they recognize it, and being wrong about which name does not undo the damage.