This check flags image files that contain alt text that is the same as the file's name.
How to set it up:
Set rule to “Flag pages that contains"
Set Search by to: XPath
Rule:
//img[@alt and @alt != '' and @src and @src != '' and (string-length(@src) > string-length(@alt)) and (@alt = substring(@src, (string-length(@src) - string-length(@alt) + 1), string-length(@src)) )]