A good rule of thumb is that companies who are at least 99% green are the most environmentally responsible. Polished plaster should be VOC-free and fully recyclable. It's important to remember that this focus on the ecological responsibility of our decorating materials not only has an impact on the world around us, but also our health.
Do you know that all the masterpieces in galleries and museums are hung on the eye level of visitors? This is around 145-152 cm from the floor. Follow the same rule, when hanging pictures in your home. If you are not sure about the choice of a right place, take a photo of the wall. You can't even imagine how informative it may be. You can mark the place, where you are going to hang a picture or even several of them to see, where they will fit better.