Demaestro - 5:21 pm on Jun 26, 2009 (gmt 0)

Don't serve a 404,

What I do it serve a "hotlink" image so that when they request /myimagebeinghotlinked.jpg they get served /anit_hotlinking_image.jpg

Then I make the anit_hotlinking_image.jpg a picture of my website with the url across it.
Or "Image Available at sitename.com"

Usually if you promote your site in the image it isn't long before they take it down.