I went into my templates>index and changed on.gif to my on.png and it never worked.
What else do I have to do?
Admin CP > Templates > Your Themes Templates > Forum Bit Templates > forumbit_depth2_forum > find .gif and Change it into .png
You'll also have to edit ./jscripts/general.js file and Change every occurrence of .gif to .png
Thanks, Yaldaram. Your a big help.