<Files somefile.html>
Order allow,Deny
allow from 0.0.0.0
</Files>
replace 0.0.0.0 with your ip.
Also if you hit google.com and do a search you will most likely come up with thousands of pages on the subject.
I can tell you that if you concern is hotlinking this won't work. Why? Well, what IP are you going to put in? Your server's? Your server is always serving the image to whoever wants it.
Your best bet is use .htaccess along with http referer. Basically you say that if the server asking for the document is not your site, bump em.
Again, hit google.com and you will find thousands of pages on this.
Hotlinking has been a big issue for many years so the resources on it are pretty built up.