For a miniature garden, furniture is a must. Even if you choose not to feature fairies in your garden you can still use furniture. The placement of a chair under a tree with a casual straw hat left behind, or a fishing rod leaning against a bench beside a pond, all makes the garden more realistic looking.
Note - the metal furniture will age and rust when used in a container that gets watered or if placed in an outside garden. To protect the furniture you can spray it with polyurethane before you ‘plant’ it in the setting.