Well, I've been battling this for a bit, and had gone back to nginx because I had some sites hotlinking stuff that they had not asked permission to do. With nginx, I was able to give them a nice litte replacement graphic instead of what they thought they were getting. 
To stop hotlinking except from domains you allow, you simply need to place this in your rewrite box
Just replace the domain names (twowheeldemon, gl1800riders, etc) with domains you want to allow and then point the images/hotlink-warning.jpg at an image you want to use that exists on your server. Should work a treat.
To stop hotlinking except from domains you allow, you simply need to place this in your rewrite box
Code:
RewriteCond %{HTTP_REFERER} !^http://(.+\.)?twowheeldemon\.com/ [NC]
RewriteCond %{HTTP_REFERER} !^http://(.+\.)?gl1800riders\.com/ [NC]
RewriteCond %{HTTP_REFERER} !^http://(.+\.)?servinglinux\.com/ [NC]
RewriteCond %{HTTP_REFERER} !^http://(.+\.)?xenforo\.com/ [NC]
RewriteCond %{HTTP_REFERER} !^$
RewriteRule .*\.(jpe?g|gif|bmp|png)$ images/hotlink-warning.jpg [L]