If you do a vermicompost toilet, the insulated tank or tanks could live there.
Bagged leaves.
Barrels of
feed.
Tree
hay.
It sounds like good place for an outdoor kitchen,except it's too low.
"Lay down yard"
Outdoor tool storage.
Compressed air tanks.
Water heater.
Kerosene heater.
Generator.
Hammock hanging spot.Probably too low
Laundry hanging spot.You can hang the cloths on pulleys.
Bug-in panic room.
You could enclose it in plastic and pull a negative pressure on it with a low wattage fan.
Rock garden.
Mushroom cultivation.
Above ground water capture/storage which
should act as a big thermal buffer.
Below ground stealth
pond.