best way to monetize hotlinked images?
 

i've got about 15k images being hotlinked. few million hits a day. could watermark a url on all of them. could redirect them all to an image advertising a url. any other good ideas?

I redirect to another image that is basically "to see this image visit mydomain.com" via .htaccess.

use .htaccess to show them a branded image or redirect them to a sponsor page with the same .htaccess.

is it possible to make a little php script that would add the watermark to all .jpg and .gif pics (for example the domain name, using gdlib) in case the picture is hotlinked?