Flowers / picnic area / benches / fountain / stall / random items that kinda make sense - that DIY bench could be pulled more central and various items placed around it - stone stools, barrels etc with items on top to look like a little outdoor workshop?
Depending on the vibe you want for your island/the area--I might put like a little cafe table and chairs with planters from looking at your path/fence/lightpost, or maybe one of the bench swings and flowers/landscaping? Or you could use some fencing and make a really cute flower patch there, I feel like that would fit in really nicely and you could use stuff like the birdhouse and whatnot to vary it up and it'd have a really cute country look to it.
My island has a lot of weird kind of esoteric statue gardens and hidden spots so for me I'd probably have a mini canal and a weird shrine of some kind xD or gravestones or something ahaha. Any chance I can build a weird waterfall cave and hide a pyramid in it, that's what I'm gonna do. So, you know, there's definitely also the pyramid waterfall cave option!