I noticed the forum is accepting large size and weighted images without down sizing etc. If the forum does not down size and compress there are going to be degradations in performance and increase in operational costs. I hit one post today that had 4 3+ MB pics in it. That 12 MB page was a slow loading page and that's with probably just one user hitting it. As more heavy weighted objects get put into the forum you will run into bandwidth issues unless you can scale your infrastructure to that of a Flickr, Photo bucket or You Tube. 100 users all hitting that page will move 1.2 GB roughly. The pages will only be as fast as the slowest link switch in the between the forum and the users PC. Heavy weighted pages will be an issue for those on slower DSL links.
If the forum re-sized and compressed the users photos to say a 1024x768 80% JPEG with compression your only in the 120 - 200KB range. Problem solved. Folks can post away and not have to worry about resizing photos themselves. If this is not an option then enforcing size limits would help.
This will conserve on Disk capacity and improve performance within your web servers, disk subsystems and network. Bottom line users get the content rich platform that is "smoking" fast providing a much better and more reliable experience. The owner and hosting provider experience a reduction in operational costs. It's a WIN WIN!
Just my 2 pennies worth.