Apparently either results.php or head.php (in view/admin/) refers to an image called small.gif by a path that doesn’t work: every time I use Search Regex I get 404 hits for a ’/images/small.gif’, when it should in fact refer to [site root]/wp-content/plugins/search-regex/images/small.gif. Apparently $this->url() precluding the path in the code doesn’t work — maybe $this is out of scope?