One of my friends converted her dining room into a mini-work out studio. My cousin converted hers to a sewing room.
How about a game room? Play on-demand ping pong or pool or even foosball like Joey and Chandler of Friends fame.
How about a cocktail lounge? Comfy chairs. Tiny tables. A player piano.
Or how about a performance space? Guitars on the wall. A karaoke machine. A stage.
Spin, people. Spin. Think outside the dining table.
Art: Still Life with Herring, Bread, and Cheese, 1858. Alexandre-Gabriel Decamps (French, 1803-1860) The Cleveland Museum of Art Open Access Collection.