When dealing with sub-forums.
It would be nice to have the ability to have a parent forum that does not have any posts (never will). But just lists the sub forums.
Currently with 7.5.3 if the parent forum does not have any posts you receive a message that states "This forum contains no posts within your specified time range.
You may want to use the form below to widen your time range."

Basically, it would be more like subcategories rather than subforums. I think this would perhaps be a decent addition.

Would be useful along with forums / categories that are links rather than forums. Always well used on other forum software, woudl like to see threads having something similar.

Well I think like this. For example you have a gallery forum.
In the gallery forum you would never have a post. But have a gallery sub-forum for each year.
So name the gallery forum xmas.
Then have Gallery sub-forums
xmas 2009
xmas 2008
xmas 2007

So you would never have a image posted in the main forum only in the sub-forums
Of course I think this should apply to all types of forums not just a gallery forum.