Try this:
AuthUserFile /dev/null
AuthGroupFile /dev/null
RewriteEngine on
RewriteOptions inherit
RewriteCond %{HTTP_REFERER} !^
http://.*domain.com/.*$ [NC]
RewriteCond %{HTTP_REFERER} !^
http://.*domain.com.*$ [NC]
RewriteCond %{HTTP_REFERER} !^
http://66.00.00.00/.*$ [NC]
RewriteCond %{HTTP_REFERER} !^
http://66.00.00.00.*$ [NC]
RewriteRule .*[Jj][Pp][Ee]*[Gg]$|.*[Gg][Ii][Ff]$ /index.html [R,L]
Coz if you get a surfer type in without the trailing slash, the htaccess sees it as not valid and won't show the pics.
The above allows .com and .com/