Shared Mailboxes' Profile Picture
Currently, changing the profile picture information of shared mailbox can be done only by using PowerShell.
Please add the function to modify the profile picture of the shared mailbox via user's browser.
There is actually a workaround: reset the password of the shared mailbox and make sure that login is permitted. Then log in as the shared mailbox in a private browser windows. Access this URL: https://outlook.office365.com/ecp/PersonalSettings/EditAccount.aspx?chgPhoto=1&exsvurl=1
You are now able to upload your desired profile picture.
deloma DE commented
This would be a good feature for users who are not using PowerShell. It would be much nicer if recipients could see an image instead of the normal letters.