In therapy sessions,  planning gets in the way of creativity; at least in my experience, that's true.  Creativity comes from feeling our way into the client's experience.  It comes from trusting the process between us. It comes from being open without a plan. Every time we do these things, we're preparing the ground for creativity.
 
Staying in contact with what is emerging moment to moment is a basic in Gestalt therapy.  Sometimes I notice spontaneous images as I am sitting with a client. I understand this to be part of our co-creation. and I try not to second-guess myself.  I just describe what I see and what it feels like to me.  Usually, it resonates and is greeted with interest.  If it doesn't, that's OK too.
 
The next thing I try to do is to stay in touch with what's concrete under abstract statements.  So, for instance, I'll ask for a specific example.
 
Staying connected to my client's integrity and identifying with the most radical parts of his or her personality helps.   I can suggest something new to try rather than talk about the possibility of something new. Here's an example that will illustrate (I hope):