There's an orphan image in prosilver/theme/images/ named "created_by.jpg". It is not used anywhere in prosilver. It is only used in one file (index.htm) in subsilver2, but it is also included in that style.
It is safe to remove it from prosilver.
Discussion topic: https://area51.phpbb.com/phpBB/viewtopic.php?t=46111