This is quick note for myself (and anybody else that may find it helpful).
When creating subforum-specific warnings, or only shows posticons to certain sub-forums (for example, as used in conjunction with posticon-enforcing plugins/products and code edits), simply use this IF statement in the vBulletin style sheet.
<if condition="in_array($forumid, array(5))">
CODE TO BE DISPLAYED
In this code example, the subforum with forumid "5" will be the only forum where, when making a new thread, that code will be displayed to a member. In any other forum (for example, subforums 1-4) the code between the IF statements will be missing.
This was used on a site where posticons are required in specific subforums. Rather than create many subforums, and requiring users to click deeper and deeper, similar-but-different content is being sorted with posticons. With this change, however, the newthread style was edited, to move the post icons above the title/message box, with a warning that you MUST select an icon. Only forums that required icons had permission to view those icons, as they were not intended to be used site-wide. (Advanced posticon permissions via plugin from vBulletin.org.) Only a single generic icon was available/used in any other subforum. Since the non-required subforums did not need such text, and it would only confuse members (since there was only one icon to "choose" from), it was hidden via this PHP vBulletin query.
Yes, that's a bit rambling -- but it's my notes. I'm allowed.
If you have questions on this specific hack/mod, simply reply.
If you need other/more vBulletin help, hosting help, web design help, etc -- post a new topic.