By structure I mean interest other than plants. This is a great time of year to look at your garden stripped! In fact all that is there are your structures and evergreens. I know, we all have sticks showing from our shrubs and roses. But structures are more commanding, they are in your face all year!
I am finally getting the idea of making a garden an extension of the home, in other words, an outside room or grouping of rooms. Think in terms of walkways, a raised bed here and there as you walk along. Think of going from room to room through an arbor or pergola. Try to vary the stone work, such as a tumbled stone for patio and walkways and a natural lannon stone for raised beds. Flag or irregular bluestone can be used for paths through arbors, etc.
In your outdoor rooms make sure there is a place to sit, or to at least look like you could sit there, a wooden bench, weathered metal or concrete. I love tuteurs (obelisks) placed in garden beds either left by themselves as decor or planted beneath with a clematis or other appropriate vine. Take it easy on the "chachkees." as they can make the garden look cluttered and take away from the plantings. If you can't pass up that concrete rabbbit or duck, have them peeking out from behind plantings.
A fence can be the frame for your garden. It can be very decorative like wrought iron and be part of the decor, or it can be woodsy like cedar and blend into the background.
Iron fencing does not have to go anywhere to enhance the garden, and sometimes they are necessary to keep large plants within bounds. Two sections together can spotlight corner plantings.
Have fun planning your outdoor room, now is the time to do it!