This bit of lighttpd configuration is what I use to stop image hotlinking, while also ensuring that search engines and social media can still access images.

smokey.conf

###Hotlinking madness :^)
$HTTP["host"] =~ "charltontrezevant\.com" {
        $HTTP["referer"] !~ "charltontrezevant|ctis\.me|google|bing|facebook|twitter|reddit|ycombinator|Skype|Slack" {
                $HTTP["useragent"] !~ "Google|msnbot|FlipBoard|Bing|Yahoo|Facebook|Yandex|twitter|Slack|Skype" {
                        $HTTP["url"] =~ "\.jpeg|\.jpg|\.png|\.gif|\.bmp" {
                                $HTTP["url"] !~ "hotlinking\.png" {
                                        url.redirect = ("" => "https://www.charltontrezevant.com/resources/images/hotlinking.png")
                                }
                        }
                }
        }
}