Check with local realtors on what will return value, or what would be a waste, and go from there, there may be things you want for personal comfort, and things that stand out.....a mini wet bar with barstools, add things like a small undercounter fridge, microwave....or even one wall of cabinets/nook for creature comforts add value.....depending on size and how much entertaining you do, size the area and set-up accordingly......adding things like an ice maker, video projector, surround sound, wether for a man-cave or family room always add value.......
we were refinancing when we changed out plans, we were just making it one big family room, and the adjuster from the bank suggested, family room, dining area, small kitchen, with 3 added bedrooms, and a full bath........nearly doubled the value of our home........
we also added a second laundry room in addition to the one on the first floor.......that was a 10,000.00 increase to value alone, and this was 2006...the extra laundry was just for me, and my little playroom....who would have thought
most perople are looking for extra space for multiple reasons, extra kitchen and laundry, guest bedrooms, even in-law quarters......all depends on what you want for now, and the future, in your home or when considering selling later on...