Maybe I'm doing things wrong here, but I have checked, and double checked and I still can't get it to work in 3.7.
I'm using the iPhorum skin as default with some tweaks.. So I changed to the default skin. Made the template changes by replacing the code. The plugin is already enabled, and imported.
I goto Forum manager, click on a sub section to edit it. Find Custom Status Icon Settings.
Set: New Posts: Replacement Image for 'forum_new' to: /community/iPhorum/customicons/cog.jpg
www.domain.com/community = my forum location
Hit save, and no change. Any ideas?