Figured I would post this here. I recently purchased a new home, and realized after a few weeks, that there was a good 40 square feet under the long staircase in the house, that was totally walled off. I discovered that the back of the stairs led to a linen closet in the master bathroom. So one day, I took a hammer and opened up the wall and peaked in with the flashlight... low and behold, TONS of space that hadn't been exposed since 1983. There were a couple of pieces of wood, and a large PVC pipe that the builders had tossed in there, haha.
In any case, I decided to lose the linen closet (it didn't make sense INSIDE the bathroom with steam, etc., plus there are already dozens of other closets) and I knocked out a hole in the side of the wall under the stairs.
This is what I ended up with. Other than the shiplap, all the other wood in there was reused... mostly left-over after I re-did my kitchen.