the features of adjectives used in imperatives with 'BE'


When you make imperatives starting with ‘Be’, they usually need adjectives, right? I think the adjectives must have some features describing attitudes or character. Be quiet/natural/positive/polite, etc., for example. Of course, in some cases in which a witch cast a spell on something, ‘Be big’ or ‘Be yellow’ can be used, I guess. What I’m saying is general situations in which imperatives are given to humans/animals.
What do you think of the features of adjectives used in imperatives with 'BE"?

By the way, another question: when a kid is blowing up a balloon, and I want to encourage him to make the balloon more bigger. In this situation, what would you say in short? Just ‘Bigger!’? ‘Make it bigger?’ Mmmm or… it couldn’t be ‘Be big’, of course. I’m waiting for your answers. :wink:

Thank you in advance,

1-- Yes, there are semantic limits on adjectives in any kind of sentence. You cannot say I have a yellow hope, either.

2-- Bigger! Make it bigger! More! Blow harder!