Currently, I have written two scripts that you might find useful:
With SSAM installed, you will be notified by email of any file changes that occur on your monitored sites shortly after the change has occurred. SSAM will detect files that have been added, removed or modified and if file permissions are changed.
‘PHP’ Find Orphan files‘ will detect if any file (image or otherwise) is referenced by any other file in the web site. It will then allow a database search for any files that were not referenced in other files. I was able to remove many image and code files from my inherited site by using this script.