RewriteEngine on
RewriteCond %{HTTP_REFERER} !^$
RewriteCond %{HTTP_REFERER} !^http://(www\.)?deine-domain\.tld(/.*)?$ [NC]
RewriteCond %{HTTP_REFERER} !^http://(.*)?google(/.*)?$ [NC]
RewriteCond %{HTTP_REFERER} !search\?q=cache [NC]
RewriteRule \.(jpg|JPG)$ http://www.deine-domain.tld/ganz-boeses-bild.png [R,L]