The sunny, flat area in the photo would be great for raised bed vegetables or you could add some low maintenance trees and shrubs for year round color. I do see the red foliage of your Japanese maple. You can add drought resistant Magic Carpet Spiraeas with gold foliage tipped in red to match. Then a weed blocking groundcover such as cranesbill geranium or kinninick  or some purple heucheras. You can still add some large tubs for growing vegetables in this sunny spot but it will not appear as empty.  To save space add a narrow evergreen such as a golden yew or for fall color a group of Orange Rocket barberries. If you want long lasting raised beds for an edible garden the metal tubs that are used for giving water to cattle are sold at feed stores and do a great job. Trust your eye, visit some local nurseries all year long to see what has color each month and enjoy the design process. It will be lovely. Keep growing, Marianne Binetti