This very much depends on personal tastes. New rugs are fresh, clean and crisp, whereas antique rugs have age-old colors and a certain cachet. Either type works equally well in both modern and classic decors, a testimony to the timeless design of Oriental rugs.
Oriental rugs come in many forms: with a central medallion or an all-over pattern; a classic or more modern look such as a Sultanabad; floral or geometric like a Serapi; complex and luxurious such as a Mohtashem Kashan or spacious such as an Oushak. Different patterns can often work with the same decor, so there is no formula for choosing a style. Nonetheless, some designs will fit better the style and any pattern already present in the room (such as wallpaper). Heavy solid furniture may work better with geometric rugs, whereas lighter furnishing could go either way; a central medallion would focus attention whereas an allover pattern would establish a more relaxed mood.
Most of the time we know instinctively where to place a rug in a room. But it is worth stepping back for a moment and challenge our preconceptions. A rug does not need to entirely fill the space, especially if the room has a nice floor. Its distance from the wall can be very flexible, although it should be at least 1 foot. What matters is the proportion of the rug to the furnishing around it. The rug can be placed under furniture, surrounded by furniture, or fully separate to admire on its own.
A hand-woven carpet can set the atmosphere in a room and create a beautiful, inviting, and intimate area.
There are a number of decorative factors to consider when choosing an Oriental rug for your interior. But the foremost criterion is that you love the rug. You like to look, step, sit, touch, and perhaps even lay down and roll on the rug. Do not choose a carpet just because it matches your decor.
Often overlooked, the texture of the rug is nonetheless an important element to consider. A silk rug for instance projects a very different look than a wool rug. More generally, the luster of the pile, its thickness, the coarseness of the grain, the sturdiness of the rug will all contribute to a certain feel.
Typically an oriental rug has up to three background colors (allocated between the field, the border, and the corners of the field or medallions if any), and from a few to a multitude of secondary colors applied to the motifs in the rug. A useful exercise is to determine first what background colors in the rug would complement those in the room, and then what secondary colors would further tie the decor.
Once this is done, one can pin down more precisely the shades and nuances that would work best: e.g., should the color be salmon-red or brick-red, strong or soft, primary or pastel, a dominant or diffused, etc.
Do not feel obliged to fill every nook and cranny in your house with an Oriental rug. Many rug dealers and interior decorators would want you to be "creative" and to place an Oriental rug in places such as the kitchen and the bathroom. That may look pretty in a magazine picture but it is not practical nor advisable. Rather, be strategic. A few beautiful Persian carpets well placed around the house can be more effective than placing a rug at every corner.
The living, family, and dining rooms are the most natural areas for decorating with Oriental rugs. So is an entrance or a large hall. You might say Oriental rugs were traditionally made for such areas, i.e., places of gathering or reception.
A corridor or a bedroom, on the other hand, are more ambiguous. We recommend to decorate these areas last after everything else is settled.