This is a basic primer on how to achieve a layered look in a room and it was born out of my lame answer to someone's question about it. I think I did a little better here.
These aren't rules but a good way to get started.
Step 1: Start with a color palette. You will build on it and away from it (explained later). I started with the muted tones in this oriental rug and chose a sofa and pillows.
Step 2: Choose various sizes and textures within your palette. You are thinking this is basic matchy-matchy decor, and it is, but this is the backdrop on which you can layer.
Step 3: Find a color outside of the original palette but stick with the same family of muted or vibrant. For instance, I would not add hot pink chairs to this room. Too vibrant. I chose a muted green and used it in two fairly large pieces.
You can also have a second color outside of the original palette that you use in various sized objects but lets keep this simple.
Step 4: Mix metals, large and small.
Varying the sizes on everything is key. Simply having several tchotchkes in brass and silver will just appear as disparate objects and not thoughtfully layered.
Step 5: Repeat a motif or texture. In this example I chose a case piece with ornate scrollwork that echos the pattern in the rug. The fact that they are different in scale and material keep them from going down matchy-matchy road yet there is enough commonality to keep it cohesive.
In a very different space you might have a lacquered piece of furniture and one or two lacquered accessories in different colors. Again, vary the size and color while repeating the texture.
Step 6: Choose various styles of art either within your palette or without.
Step 7: Add real life accessories. I think this is the most important element. I added a stack of books to illustrate this but you should be much more creative with it. On a hall table your "key bowl" could be an interesting thrift find. A throw made by your grandmother or a clay piece made by your kids adds the one-of-a-kind personal layer to a room. These items need have nothing to do with the other colors and textures. They are the imperfect touch that individualizes a room.
Go forth and layer!