SharePoint offers 3 options for User Profile and Property synchronization.
1. SharePoint Profile Synchronization
2. SharePoint Active Directory Import
3. External Identity Manager
I won’t go into the depth of each, but let’s say you choose SharePoint Profile Synchronization to import Active Directory information including the Picture.
Now after syncronization, you need to run this SharePoint Powershell to convert the imported pictures into the small, medium, large sized photos that can be used properly.
Update-SPProfilePhotoStore -CreateThumbnailsForImportedPhotos 1 -MySiteHostLocation http://mysitehost:port/sites/people/
Now, it seems maybe not all PictureURL properties got imported and converted, and you have to start again.
Instead of deleting the user profiles (and potential data entered by the user), here is a quick and easy way to clear out the PictureURL property from all user profiles.
$site = Get-SPSite http://mysitehost:port/
$context = Get-SPServiceContext $site
$upm = New-Object Microsoft.Office.Server.UserProfiles.UserProfileManager($context)
$upPictureURLAttribute = "PictureURL"
$profiles = $upm.GetEnumerator()
foreach ($userprofile in $profiles)
write-host "Deleting ", $userprofile[$upPictureURLAttribute].GetValue()