To make a room cozy, essentially you are saying that you want a more intimate space. You can do this by creating zones within the room. Create a place for two people, this creates a more intimate area. You can also furnish it with softer features. Remove solid looking furniture and introduce softer furnishings, like ottomans or bean bags. In terms of flooring, wood flooring alone can look harsh, introduce a large, warm rug that softens the room. Wall color is very important. Cold colors like white do not help, introduce a warmer color palette.