MigrateOffice365PhotosToAD.ps1

function Get-Office365Photo($EmailAddress,$Credential) {
    $wc = New-Object System.Net.WebClient
    $wc.credentials = $Credential
    # Build the URL that'll return the jpeg of the user's photo
    $url = "https://outlook.office365.com/ews/exchange.asmx/s/GetUserPhoto?email=$EmailAddress&size=HR96x96"
    # Build a path to export it to (.\kim.akers@contoso.com.jpg)
    $outPath = "$pwd\$EmailAddress.jpg"
    try { 
        # Download the image and save it to the current directory
        $wc.DownloadFile($url,$outPath)
        return $outPath
    } catch { throw $_ }
}

function Upload-ADPhoto($Username,$FilePath) {
    # Import the photo into a variable as a byte array
    $photo = [byte[]](Get-Content $FilePath -Encoding byte)
    # Replace the current value of thumbnailPhoto with the byte array from above
    Set-ADUser $Username -Replace @{ThumbnailPhoto=$photo}
}

# Get the credential to allow us to download the images
$Cred = Get-Credential -Message "Please enter your Office 365 Credentials"

# Get every mail-enabled AD user
$users = Get-ADUser -ldapfilter '(mail=*)' -properties mail

# For each of the mail-enabled users...
foreach ($user in $users) {
    try {
        # Download the photo
        $photoPath = Get-Office365Photo -EmailAddress $user.mail -Credential $Cred
        # Upload the photo
        Upload-ADPhoto -Username $user -FilePath $photoPath
    } catch {
        Write-Warning "Unable to update image for $($user.mail)"
    }
}