Add an icon to custom admin menu (WordPress)

Hello, my theme implements an admin theme-menu called Theme-options in Appearance, I am not sure if I can add an icon (via CSS or JS) to this menu, if I do this will the reviewer reject my theme? Anybody can give me some suggestions? Thanks!!!

As long as you follow the WordPress Upload rules, you can modify and add the theme-options menu.

Many thanks for your help!