Javascripts - good idea, but bewarned....

It's still extremely easy to get the picture. Many people 
don't surf with JS enabled. Many hard-core surfers like me 
use the right-click to navigate (reload, back, new window, 
add bookmark). When I run into a site like this - I don't 
care for what reason, I'll hit 'back.' Source code (or Page 
info) is the Achilles' heel for this. 

If you're really concerned about people taking an image 
from you - bottom line is you should not post pics at all.
A sad truth of the internet.

IMNSHO, physical stamping and watermarking of creative works
is the best way. ^_^ (And in an earlier post, to prevent 
cel hijacking on EBay, don't scan the registration holes & 
numbers....)

Good luck