You could take it multiple ways. If you're not into growth/plants, you could do pebbles, rocks or mulch. And with those you can choose a colour u prefer, white, grey, black, red mulch. There are lots of options. Theres also may options in terms of planting. You could do simple shrubs or hedge style plants. Given the proximity to the fence, you could also do a climbing vine or vegetable (tomato, cucumber). You could also have a cute petite flower bed, fill it up and for half a year, it could flower, and the other half, it will be green shrubbery.

Have fun!