IMHO (and very humble one that is
) cPanel's default icons are very conservative. This is not a complaint because when I fire up the control panel, I am often eager to get jobs done, and so I don't notice the icons very much -- in a way it is good that they are not distracting my work.
I think though, to make a difference, they should revolve around a theme, for example, glossy images (I hate them -- but it's a valid theme). Only if the changes are consistent as a whole, will users feel the difference in icon (re)design. The theme can also be a colour choice, for example, black and red. If all icons have prominent black and red, that would surely make a difference.