Oh ok, you only use that site, not run it. Your first post makes it seem like your running the site.
Hot linking is bad when it's not a site or bandwidth your paying for. That's why a lot of free host providers do not offer such services, they're paying the bill, not you and most of the time ads don't fully pay for all the services. When you start hot linking for pictures and such, their bandwidth goes up.
I'd just recommend hosting your own images if at all possible. It's just the most ethical thing to do.