Hi @Talya Shalev ,
Have you tried a user logging out of Teams and back in? If users have been using Teams for some time this could be due to the Teams client caching:
http://www.matthewjbailey.com/solved-microsoft-teams-profile-picture-not-showing
This is also discussed over here:
https://techcommunity.microsoft.com/t5/microsoft-teams/team-picture-doesn-t-show-up-for-any-users/m-p/828768
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Best regards,
Leon