The Forumdisplay uses the old GIF file and not the newer PNG files for when there is a subforum.
There issue is visable in the pt_subforumbit_project template.
It also doesn't currently load up the status of projects held as child to the parent forum when they would list as subforum level on the main forumdisplay, but it does when viewing the immediate parent forum.
All images are currently .gif, and we will be converting them to .png.
Not the case throughout. When looking at a forum which has child forums, it uses images/statusicon/project_forum_old.png or the new one.
The icon used in forum listing is the image name you posted (project_forum_old.png) which is the latest and will not have a newer as it's in accordance with the vB4 style.