Well I would make sure that all files etc are maintained with permissions as noted here
PhotoPost PHP Photo Sharing Photo Gallery Installation Guide
One word of caution though. While there are no reported ways to break the photopost script tieing it to vbulletin that has hacks/mods can open up exploits. I always suggest running stock sites and not using code posted by others.
Like there was one reported post where users found .php files throughout the data folder of photopost and Michael himself at one time was a victum of this and it came down to a flashchat for
vb Michael has installed. Once your ftp or some other file is compromised users can easily alter any file that is writable on the server or any directory.