I believe that if you get a suggestion from the audience, every suggestion is useable.
It´s up to you as an improviser to be able to look at the suggestion with the eyes of different persons, persons from different professions.
If the suggestion is “The Weather”, the meteorologist will have a different story than the farmer, and the scientist studying microorganisms in the deeper soil layers on the Island of Man will have a completely different narrative.
If the suggestion is “Wool Socks” the meteorologist, the farmer, and the scientist will have their stories to tell, and a mother of twins will have yet another story/narrative to tell.
And further if you let the scientist and the mother have a relation, and you improvise a scene were they to start with stick to their individual their personal opinion on wool socks you might have the starting point of a scene.
This ability to look at things from the perspective of different profession can be developed by a few minutes of practice every day.
Wherever you are there are things to look at from different points of view, and I am sure that during the day there will be moments where you are waiting. So why not have fun waiting and at the same time expand your “library of possibilities”(note 1).
Right now, I am looking out my window, and there on a balcony is a bucket filled with yellow flowers.
The first thing that pops up from my “library of possibilities” is: As a bee I would follow my instinct that tells me nourishment. And now it is a vegetarian wondering if they are eatable. And now it´s a widower going to bring flowers to grave of his deceased wife.
All these came easy. So why not challenge myself and see if there is something hidden in a dusty corner of my “library of possibilities”, something that I didn´t know “I know something about!”. Ok, what comes into mind is “a Nail”, and now since I´ve been working as electrician, I have a hammer in one hand and the nail in the other, voila the nail sits in the wall, I tie a string around the flowers and hang the bouquet on the nail.
This a lovely way to expand your creative capacities, it´s a basic tradition and practice in the world of creativity to connect things that at first seem without any kind of connection.
So, any suggestion will it be from the audience or some character on stage is usable when you respond to it with a point of view or attitude.
Note 1. “Library of Possibilities”, this is an expression/ image I use for our unconscious, I call it a library to make it to easier to access, to take away the clouds of mystery and danger.