If you want to allow your users to attach larger images (file size), fix your "Forum Group Permissions" "Max file attachment size" settings to allow your users to attach larger file sizes.
The Max file attachment size permission = the file size of the file that is allowed to be received by your forum BEFORE having any type of resizing or compressing done to it.
The image compression and resizing can only be done to the image once it has been received by your forum.
