Jun 20 2019 06:09 AM
You can add photos to Azure Active Directory guest accounts and have Office 365 apps display those photos. But it's a lot of work to track down suitable photos for individual guests. If you want to change the default two-initial icon displayed by Office 365, you can use PowerShell to update all guest accounts with a photo. Here's how I handled the problem.
https://www.petri.com/add-default-photo-azure-active-directory-guest-user-accounts