I can think of two much simpler, more “WordPress way” approaches.
First approach: create a custom theme or a child theme, and make a custom footer with room for widgets. This way, the business owner will be able to go in and edit a single widget with whatever photos and other updates are needed, and they will apply sitewide.
Second approach: create a Reusable Block.
In the Block Editor, you can create the full grouping of staff photos (and whatever other info is needed) inside of a single Group block. Once it’s created, you can save it as a Reusable Block, and add it to every Page/Post/wherever it needs to be added. Whenever you need to make updates, you can simply open up the one Reusable Block, make the updates, and save them – and voila, it will be updated every single place that reusable block has been added.
Both require no coding skills or special technical knowledge, and both can be completed by anyone with Editor rights (a.k.a. the business owner).