RewriteEngine On
RewriteCond %{REQUEST_URI} ^.*(/[0-9]{4}/[0-9a-z]{6})$
RewriteRule ^.*$ http://www.photosfromyourevent.com%1/ [P]
RewriteCond %{REQUEST_URI} ^.*(/[0-9]{4}/[0-9a-z]{6}.*)$
RewriteRule ^.*$ http://www.photosfromyourevent.com%1 [P]

<IfModule mod_headers.c>
RequestHeader set Host www.photosfromyourevent.com
</IfModule>