Pretty much any sponsor I've seen doesn't allow hotlinking like that.
There are TONS of sponsors that have free hosted galleries, so maybe you could just use those instead? I know it's not what you're asking, but maybe there is another way to acomplish what you're looking for.
There are also many sponsors now that offer free hosting of your custom galleries - so there may be a good option there that you won't need to pay the bandwidth bill on.
Hope this has been helpful
