For drapes that look rich and luxurious, keep these three tips in mind:
1) It all starts with the fabric. Unless you have specifically gone for an airy look and are using sheers, gauze, or tulle, luxurious drapes start with a fabric that have body. It's kind of like hair - you don't want limp drapes. The material should have some umph. It doesn't necessarily have to be stiff, soft fabrics flow and fall gracefully, but it should have enough strength to hold it's pleats and shape as it hangs. Notice in the picture above how nicely the pleats hang, even the long, heavy panels. (Click the picture for a larger view.)
2) Fullness. You want sufficient fullness in the drape. At a minimum, you should use one and a half times the width of the window for a gathered drape or valance. Twice the width is much better. You can see the fullness in this drape in the long panels by the number of pleats and in the jabots on the corners. The valance itself is straight, but the fullness is still there in the other elements. Even if you pull the drapes fully shut, there should still be some additional fullness - think of pleated drapes - even when closed the pleats add fabric to avoid creating a window covering that looks like a single sheet of material.
3) Layers. For the most luxurious window treatments, use layers. Sheers or underdrapes. Valances. Panels. Overpanels. Blinds, shades, or shutters. Use good taste, but you'll often see three elements: a privacy layer, a top such as valance or cornice, and panels or swags. Here you'll see two layers although the jabot adds a nice touch on the corners. I would recommend blinds or shutters for privacy and to block out the lovely view of the neighbor's downspout and chimney chase.
And here's another bonus tip - embellishments. Trims, rosettes, fringe. Currently drapes are shown with adornments such as these. Granted, you can overdo anything, but if tastefully done and complementary to the fabric and the room's decor, these features will have your window treatments screaming "luxury."