Unless you have some kind of restriction placed on hotlinking, you should be able to link directly to the image from the forum. You will need to look at the FAQs of the forum itself to figure out how to reference the images. There shouldn't be any need to do anything special to make this happen.
Be aware that unless you have the images cached, each time they are accessed by the forum, it will eat into your bandwidth allocation.
Simon Jessey | Keystone Websites
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