Hi Joshua,
where else are the pictures shown, when not on the page where the post is made?
if you mean, you want the pictures not linked, but uploaded directly to your forum, then better think twice about it. I don't know what kind of hosting contract you have, but at first, when all the pictures are uploaded to your webspace, then you can get very fast some space problems. Perhaps not in the moment, but when your site grows bigger in the same speed you will get one.
and secondly, much more important: it is your webspace. that means you are personally responsible for all files, that are on your webspace. when someone thinks, it is a good idea to upload pictures with illegal content, then it is in the end your problem.
ahhh, and not to forget, the classic thing. it is very easy to use pictures to hide stuff. so in the pictures can be hidden stuff like viruses or root kits.