The secretary, like I stated before could have a small lamp, a book, ivy or picture frames. The built-in is a different story. You will need to fill these things with something. A stereo and speakers will fill part of it. I assume a CD collection will fill part of it.
Books are a wonderful way to fill space.
But be sure to add some interest with things like picture frames, small plants, glass pots, pottery bowls, trinkets, figures. I know you don't want things to dust so don't use a lot. Have a variety but make books and the stereo the majority of what is there. For those days when it is cool outside and rainy and all you want to do is curl up by the fireplace and day dream, you need a sofa throw. It should be green or cranberry in color.