The right text can make or break a sig/banner. But there's something to be said for the minimalist approach too. The right picture(s) editted in the right way, and having just the right part cropped/showing. That can have an impact on its own. Text is usually just icing for me. If its good icing, it can make it better. If its bad icing, it can make the whole thing crash. But some cakes don't necissarily need icing (I guess)