Using Zenity is possible to add buttons,change fonts ,anything besides default options? If not,there's another dialog for sh that allows more customizing?
Zenity supports a few HTML-like tags for text markup: <b>, <i>, <u>, <s>, <tt>, <big>, <small>, and more -- well, really it's Gtk+ that supports those tags, but Zenity gets to piggyback on top of those features.
For more control over your dialogs, you can intead use Kommander. It's like a form builder compatible with all sorts of scripting languages: Python, Perl, Ruby, shell. There's various examples out there.