Ok.
Can you please provide your forum URL?
What you need to do is go back to Admin CP > Membergroups > Modify (whatever membergroup it is that you're trying to change the image for)
And put this in the box next to Star image filename: 1staraqua.gif
Then click save. Go back to Admin CP > Membergroups and make sure that the image shows up next to the name of the group there.
Then put that code in your footers.