Change your profile picture in Teams
To change your profile picture, click your current picture at the top right of the screen and then click the camera icon that appears when you hover over your profile picture.
From the menu that appears, click Upload picture to access your photos.
Note: Teams users with mailboxes hosted on premises must be synchronized to Azure Active Directory. They can change the user profile picture providing Exchange Server 2016 (Cumulative Update 3), or above, is running on-premises. For more details, see How exchange and Microsoft Teams interact.