Can be achieved by placing 4 different Hipster style furniture pieces, it doesn't matter what type (can be kitchen, chairs, art) as long as it has the Hipster indicator in the game.
Hipster furniture is the first to research at the Decoration Shrine and only costs 100 delight.
The game will state if you already have 1 of an item and that the stats won't go up, i.e.; have 2 Hipster chairs of Hipster: 2 stat, is not 4 stat, it's 2 stat.