A small nook with a light, pillows, shelves, and drawer storage. Not only is it relaxing but it would make great use for the space under stairs, especially in a finished basement. It also looks comfy enough for children to use for sleep overs or severe weather.

26 Incredible Under The Stairs Utilization Ideas

Laundry Under Stairs

25 Clever Under Stairs Ideas to Optimize the Leftover Space

Make use of that space under the stairs, and make a mini utility room! Just place a butchers block workbench over the top of your washer and add a shelf for extra storage.

On wheels is cool if closed in storage "over" stairs - Google Search

Such wasted space above the basement stairwell. It appears as though this shelf is on wheels to bring forward for better access.