You can store anything there that can withstand frost, heat, and moisture. Tiles, roof tiles, suitcases, etc. But neither paint nor fabrics nor sensitive electronics.
And there we have it already. Old paint cans with paint, clothing, boxes, Christmas tree stands and Christmas decorations should already be stored there. Let's see how expensive it will all be.
You can store anything there that can withstand frost, heat, and moisture. Tiles, roof shingles, suitcases, etc. But neither paints nor fabrics nor sensitive electronics.