Board Thread:Support Requests - Community Management/@comment-4904721-20140105225833/@comment-4784321-20140105230228

Dead files? Do you mean files that have been deleted?

Since those do not have File in front, I do not think the file option will work with galleries. So, you will need to go to Options -> Find and replace -> Normal settings and then enter the file name (without File:) in the find place (such as EvergreenFir_Avatar.png). Leave replace with empty.

Another alternative (can delete all files in WantedFiles at once, but has bugs) is pywikipediabot. (Guide).