[Mr.Byte]

You can replace the bottom ones by replacing the images in your images folder named
"on.gif" "off.gif" "offlock.gif" It may have a different extension to the end.

As for the other icons, you can install a forum icons plugin, this will allow you to set an icon for each forum.

If I change that... only icons will change ... the forums icons will be remained.
I want to change it completely
Thanks