The sense of peace and quiet moments often happens around us in our daily lives without us noticing it. Even in some real chaotic circumstances there is tranquility to be found. If you are inspired beyong words, if you see the beauty of the moment, if it is resonating in your inner most like a beautiful sunset, a perfect sky, a flower swaying in the breeze - these might be things to put in an image about stillness. But taste is different and it might be something else for you.
At least it is in my opinion something which gives you the feeling and opportunity to pause, reflect, hold on to an emotion, feel the simple joy, wander in your memories and give peace to your soul.
To see images like this, as always in photography, observation is the main key point. Discovering your vision of everyday moments in images that evoke a quiet, calm feeling is not as difficult at it might seem in the beginning. This kind of image can be found anywhere.
Perspective and showcasing your favourite still images will have a distinctive influence on the Emotion emanating from them. think out of the box, think in squares, think in colour, think in .... whatever you feel. To suggest tranquility, at least in my view, is the distilling in the frame the essentials in a deliberate simplicity. Capturing this moments the details are the things thats matters most. Using depth of field in capturing them. Distilling a single point of importance, isolating it from the background and accentuating its delicate and subtle details is surely one way to go.