In response to your comment here, uploading a PSD file to your FTP will not do anything. To replace the forum icons you mentioned, you need to save your custom icons as .PNGs (forum_new-48.png, forum_old-48.png, forum_old_lock-48.png, forum_new_lock-48.png, forum_link-48.png were you ones you mentioned) and upload them to /images/statusicon/. Let me know if you need any other help!