Board Thread:Support Requests - Getting Technical/@comment-4220590-20170528101115/@comment-15278555-20170528150519

AWB cannot access a lot of the special pages including Special:UnusedImages. I and others have asked for this to be added but as of yet they haven't done it and since the WMF is currently designing a web version of AWB similar to the one Joey created, it's unlikely to happen any time soon.

There are several workarounds if you want me to explain some ways you can still do this in AWB but it sounds like a couple good suggestions above already.

A word of warning though if you do delete these. I have noticed in the past that the Special reports isn't always accurate and doesn't always reflect those images that truly aren't used. So even though some might show as not used, they really are on a template or something that doesn't show the count due to the way it's transcluded.