Unless you’ve perfected the art of the paperless office, you’ll most definitely need some storage space. Buy big boxes, label them well and then find a place to hide them away; maybe doubling up as a home office chair.
Use coloured folders for storing things like receipts, bank statements and bills.
Speaking of colour, leave space in the office for some plant life. Research shows that having green flora in the office helps humidity levels, makes you more productive, and reduces any feelings of isolation.