I'm starting using emacs. I know that everything of emacs is customizable. But, one thing I can't even found on internet is modifying the default emacs' widget's Look and Feel.

Is there some way to custom it's background, shape, etc or just using UTF-8 character (for example checkbox using ? character)?

Well, as a new user, I was quite boring with the customize interface. Some kind of

I want to change onto a flat-styled ui or a better one.