In this situation, you could use small rocks, flowers, patches of grass, or you could even make small buildings that don’t have to have a purpose (shacks, houses, etc)
As for the ocean area, you could probably use some slightly larger rocks sticking out of the water, as well as a shipwreck or some lilypads
In addition to what @Advareo said, I’d say bigger and different variations of trees. Maybe more biomes if you are willing to do that with this area. Beach, mountain, hills, ect.