Pillow room: don't spend money on couches or lounge chairs and buy a really nice movie screen. (This would be really fun for movie night, to just move all the living room furniture and bring out the pillows!
THE SPACE / EXPLORE / BUILD rock pillows. When I was a kid, our basement was all pillows, blankets and matresses. Me and my brothers would play for hours. Great memories, and ones I want my kids to have