https://ubbwiki.com/wiki/view/91/attachments.html Settings for image uploads
• Navigate to "Display Options" -> "General" in the UBB Control Panel.
• Select the Topic Display Options Section to expand it.
• Add a value for "Max Size" for "inline uploaded images".
If an image is attached to a post, if it is smaller than the specified size (in bytes), it will be displayed in the post. This value is entered in bytes so for a 1 MB file you would enter 1048576; if the file is larger than what is entered it will display as a link.