These can be something as simple as a goddess sculpture or as specific as a statue of St. Francis of Assisi. This choice of image must be evocative for the user personally to make the space is equally as intimate and meaningful. Often the entire garden is focused upon the image, much the same way that altars are arranged in places of worship. To take full advantage of the psychological benefits of a private sacred garden, you must be comfortable there. This requires furniture of some type for sitting or reclining.
Comfort also relates to environment.
If you live in a very hot, inland region, be sure there is plenty of shade in the private garden. This can be permanent such as an overhead arbor. This structure can be fitted with either an outdoor ceiling fan or a misting system for evaporative cooling where the air is dry. For winter you can incorporate an outdoor fire place or fire pit. Consider a large ceramic outdoor oven that is both safe and moveable.