Not that I have an empty closet, but i do like this."Closet Office" - Turn your un-used closet/reading nook into an office space. Maximize the little space with lots of shelving and storage *LIKE CORNER DESK/nook & shelving for office corner
This is a perfect combo of my two favorite ideas for that space under the stairs leading to the basement. A reading nook AND book storage and shelves . assuming that there is enough space for this there.