pic from Real Simple
In this pic, they are using a suitcase to store sheets and other linens. I have a friend who lives in an older home and does not have a linen closet. This would be a good use for her luggage. And since she keeps her luggage stored under her bed, it would also be a great place to store off season clothing or shoes.
If you had older, vintage, "cool" looking hard sided luggage, like those in the pic, you could also stack them and use it for a nightstand, a conversation piece coffee table, or other side table in a room where it would fit the decor.