Add-ThumnailPhoto

https://support.microsoft.com/en-us/help/2497721/user-contact-photos-in-lync-aren-t-displayed-correctly

#If you are running the Microsoft Azure Active Directory Sync Tool , 
#run a Windows PowerShell script to populate the thumbnailPhoto attribute in the on-premises Active Directory schema. 

$SAMName=Read-Host "Enter a username"

#input variables
$root = [ADSI]'GC://dc=contoso,dc=local'
#On line 2 of the script, edit the GC location to reflect the local Active Directory schema. 
#In this example, we use the Contoso.local domain. 

#script variables
$searcher = new-object System.DirectoryServices.DirectorySearcher($root)
$searcher.filter = "(&(objectClass=user)(sAMAccountName=$SAMName))"
$user = $searcher.findall()
$userdn = $user[0].path
$userdn = $userdn.trim("GC")
$userdn = "LDAP" + $userdn

function Select-FileDialog
{
param([string]$Title,[string]$Directory,[string]$Filter="All Files (*.*)|*.*")
[System.Reflection.Assembly]::LoadWithPartialName("System.Windows.Forms") | Out-Null
$objForm = New-Object System.Windows.Forms.OpenFileDialog
$objForm.InitialDirectory = $Directory
$objForm.Filter = $Filter
$objForm.Title = $Title
$objForm.ShowHelp = $true
$Show = $objForm.ShowDialog()
If ($Show -eq "OK") {
  Return $objForm.FileName
  }
Else {
  Write-Error "Operation canceled by user."
  }
}

$photo = Select-FileDialog -Title "Select a photo" -Directory "%userprofile%" -Filter "JPG Images (*.jpg)|*.jpg|PNG Images (*.png)|*.png"

$user = [ADSI]($userdn)
[byte[]]$file = Get-Content $photo -Encoding Byte

# clear previous image if exist 
$user.Properties["thumbnailPhoto"].Clear()

# write the image to the user's thumbnailPhoto attribute by converting the byte[] to Base64String 
$result = $user.Properties["thumbnailPhoto"].Add($file)

# commit the changes to AD 
$user.CommitChanges()

#write results to output
if ($result -eq "0") {
  Write-Host "Photo successfully uploaded."
  } 
else {
  Write-Error "Photo was not uploaded."
  }

#Wait 12 to 24 hours for all changes to take effect.
#Note If the photo was published by using this method, external contacts such as Hotmail users and other federated organizations 
#can't display the photo. The photo can't be displayed because the file can't be accessed from external locations.