Design seating that allows the listener to enjoy what he is hearing. The chairs need to be comfortable if the listening session is for a long period of time. Since you will be placing speakers in many areas of the room, the seating doesn't need to be too tall as to block the sound coming from behind or from the sides. Place just enough chairs to fill the room, but be weary of how a full room will affect the acoustics as well. Place just enough to minimize the effect of the room's guests.
There are many materials you can use on the walls, floor and ceiling. Depending on how much control you would like in regards to the sound, you may choose to deaden the room. To do this, use a material such as fabrics or panels made with foam and fabric, which will eliminate standing waves and frequency overlap. You also want to use carpeting on the flooring as well.
To have a listening room that is bright, you may want to have marble flooring and nothing on the walls other than artwork or framed photos. This will allow the sound to bounce around and have an airy feel. Many prefer the hollow sound of a lively room to an acoustically dead room.
To listen to anything, you will need an audio system for playback. This can vary from home audio quality to audio equipment used in recording studios. These items should be built into the room, and cables should be neatly hidden in alcoves or fed through walls. In designing a listening room, the sound system needs to be permanently installed. Further, make sure there is room for expansion as electronic devices often become obsolete rather quickly. There needs to be space for at least five speakers and multiple power amps as well as a CD player and MP3 player for reproduction.