Topiary is a great plant for structure because it can be made into any shape you like! Good plants include box, yew, bay, ilex, and conifers.
Plant topiary balls, cones, spirals, or lollipops for striking evergreen focal points. Alternatively, if you’re feeling brave, you can create your own shapes. You can cut freeform, but I recommend using a topiary frame, which is a wire mesh shape that you place over the plant as a 3D template.
You can even buy animal shapes like chickens!