If you have statues, you should not discriminate between them on the basis of their materials, and you must arrange them in a proper order. Even if a statue of a buddha is made of clay, it has to be placed on a high level; and even if your statues of dharmapalas such as Mahakala are made of copper or brass or even solid gold they should be placed below. The proper order should be maintained. Especially, you should not have the attitude of their being your possessions. Although there are statues that were once owned by great beings and so forth, and that might have special power or sacredness, irrespective of their age or sacredness they have to be placed in the proper order. The whole purpose of regarding them as sacred is that they are to remind us of the actual deity or being that they represent. It is not the statue or the picture that we hold dear and venerate; rather it is what it represents. When we buy images of the Lord Buddha, it is to generate faith, because when we see them we recall his great kindness and qualities.
Also, as a representation of the omniscient mind of the Buddha, it is good to have a stupa.
If you are a practitioner of highest yoga tantra, it is good to have religious articles such as vajra and bell and so forth; but if you do not practice properly but ring the bell very loudly and violently it does not help much! If you keep these religious objects on the basis of a good practice it is excellent.
Generally it is said that when one undertakes a dharma meditation, one has to face toward the east, but this is not very important. It is good to have a seat with the rear slightly raised. For Westerners it may be difficult to sit in a cross-legged position. If you insist on it and exert yourself trying to do it, you might expend all your energy in sitting cross-legged, and there is a danger of all your mental energy going to your knees. Therefore, you can sit on a chair.
Since the accumulation of merit through the mandala offering is very important, it is good if you have a mandala. If you can afford it, it is better to have one made of gold or silver, but such things should not be viewed as possessions. If the material from which such articles are made were important, then such meditators as the mahasiddhas and Milarepa would not have achieved any realizations at all because they were poor, just like beggars. It is explained in Chatu-shataka Shastra (Four Hundred Verses on the Middle Way) by Aryadeva that the practice of buddhadharma has to be undertaken on the basis of the mind, and therefore the external things are not important; it is the mind which matters.
Adapted from The Union of Bliss and Emptiness: Teachings on the Practice of Guru Yoga by H.H. the Dalai Lama