param([string]$url, [string]$siteLogoUrl, [string]$description)

$spAssignment = Start-SPAssignment

$spWeb = Get-SPWeb $url -AssignmentCollection $spAssignment
$spWeb.SiteLogoUrl = $siteLogoUrl
$spWeb.siteLogoDescription = $description
$spWeb.Update()

Stop-SPAssignment $spAssignment