Tibetan Religious Symbols
It is common to see various religious symbols when traveling in Tibetan monasteries, villages. They are used as sacred adornments.
The Eight Auspicious Signs, or eight motifs, generally symbolize how to progress along the Buddhist path.
White Umbrella: a symbol of loyalty and faith and Dharma protection from all evil.
Golden Fish: a symbol of happiness, soul emancipation, and salvation from the sea of suffering
Vase: stores the nectar of immortality and symbolizes hidden treasure
Lotus: symbolizes purity and spiritual enfoldment
Conch Shell: proclaims the teachings of the enlightened ones and symbolizes the spoken word.
Knot of Eternity: symbolizes the unity of all things and the illusory character of time.
Victory Standard: the cylinder symbolizes the victory of Buddhism over ignorance and death.
Dharma Wheel: symbolizes the unity of all things, spiritual law and Sakyamuni himself. The wheel is usually flanked by two deer, the first to listen to Sakyamuni's teachings. The male deer symbolizes the realization of great bliss while the female deer symbolizes the realization of emptiness.
Other common symbols:
Swastika: commonly seen on home walls or on monastery floors. Meaning good fortune, it symbolizes infinity, universe and sometimes sun and moon. Buddhists draw it clockwise while bon followers draw it anticlockwise.
Kalacakra Seal: an adorning motif in murals or on monastery walls. It symbolizes the highest initiations into occult knowledge which can only be possessed by a few high lamas.
Wheel of Life: in murals or on monastery walls. The demon of impermanence holds a wheel, segmented into six sections, which mean all realms of existence respectively. These are: Heaven, demigods, humankind, hell, hungry ghosts and animals. The hub in the center symbolizes ignorance, hatred and greed, the three poisons.
Sun and Moon: usually seen on village houses and top of stupas. The adorning motif symbolizes the source of light and union of opposites.
Mani Stone: 
Travelers to Tibet may find mani stones and mani stone mounds almost everywhere, in monasteries, beside villages, along paths and on mountains. Sometimes they are decorated with sheep and yak horns. Usually the universal mantra, Om Mani Padme Hum, is inscribed on these smooth stone plates, pebbles and rocks. Images of deities and great adepts and sutra texts are also common themes. Tibetan people build these unique works of art to show their piety to their deities and the Buddha's teachings. Upon encountering a mani stone mound, Tibetan people circumambulate it clockwise as a prayer offering for health, peace, and protection.
Prayer flag:
The fluttering prayer flags can often be found along with piles of mani stones on rooftops, mountain passes, river crossings, and other sacred places. Prayer flags are actually colorful cotton cloth squares in white, blue, yellow, green, and red. Woodblocks are used to decorate the prayer flags with images, mantras, and prayers. Usually at the center of a prayer flag, there is an image of the Wind Horse which bears the Three Jewels of Buddhism. On the four corners of the flag, are images of Garuda, Dragon, Tiger, and Snow Lion which are the four sacred animals representing the four virtues of wisdom, power, confidence, and fearless joy respectively. Sometimes auspicious Buddhist symbols can be found on the edges. In the blank spaces between the images, prayers and mantras are printed. There are two kinds of prayer flags, the horizontal ones called Lungta in Tibetan and the vertical ones called Darchor. Horizontal prayer flags are squares connected at the top edges with a long thread. The less used vertical prayer flags are usually single squares or groups of squares sewn on poles which are planted in the ground or on rooftops. Tibetans believe the prayers and mantras will be blown heavenward as offerings to their deities and will bring benefits to the one who hangs them, his neighborhood, and all sentient beings, even flying birds. However, if the flags are hung on the wrong astrological dates, they will bring only negative results. And the longer it hangs, the greater the obstacles which will arise. Old prayer flags are replaced with new ones annually on Tibetan New Year.
Prayer Wheel:
Prayer wheels, called Chokhor in Tibetan, are very common religious objects in Tibet. A hand held prayer wheel is a hollow wooden or metal cylinder attached to a handle. Om Mani Padme Hung mantras are printed or etched in relief on the cylinder. Attached to the cylinder is a lead weight with a chain, which facilitates the rotation. Tibetans use prayer wheels to spread spiritual blessings to all sentient beings and invoke good karma in their next life. They believe that every rotation of a prayer wheel equals one utterance of the mantra, thus the religious practice will in return help them accumulate merits, replace negative effects with positive ones, and hence bring them good karma. The religious exercise is part of Tibetan life. People turn the wheel day and night while walking or resting, whenever their right hands are free while murmuring the same mantra. Buddhists turn the wheel clockwise. Bon followers turn the wheel counter clockwise.
Prayer wheels vary in size and type. Not all prayer wheels are hand held. It is common for bucket-sized prayer wheels to be lined up on wooden racks along walking paths circling monasteries and other sacred sites, for the benefit of visiting pilgrims. Larger water, fire, and wind prayer wheels are built so that they are empowered by the flowing water, the flaming light, and the blowing wind which drive them, and can later pass their positive karma to all who touch them.
Tangka:

Thangka or scroll paintings are sacred artifacts used as physical support in Tibetan Buddhist practices. In Tibetan the word 'than' means flat and the suffix 'ka' stands for painting. The Thangka is thus a kind of painting done on flat surface but which can be rolled up when not required for display. It is either painted or embroidered and is generally hung in monasteries or a family altar and carried by lamas in ceremonial processions. The pictorial subjects of thangkas include portraits of Buddhas, stories from the lives of saints and great masters.
To Tibetans, the art of thangka is apocalyptical. There is room for the individual painter’s creativity only in case of the details of the landscape, the color and shape of the cloud, of rocks and flowers, etc. But what actually illuminates the artifact is its visionary quality. The mystical thangkas are supposed to be the records of visions in all its sensuous details. The Tibetan artist, being concerned primarily with life, death and the life to come, finds it his duty to embody the vision of the life yet to come and thus assist others in their journey towards Nirvana.

Om Mani Pedme Hum: Om Mani Pedme Hum (or Om Mani Pedme Hung), is the most common mantra in Tibet, recited by Buddhists, painted or carved on rocks, prayer wheels, or yak skulls and seen around most usually. Tibetan people, almost all Buddhists, do believe that it is very good to practice the mantra of Chenrezi, the Bodhisattva of Compassion (The protective deity of Tibet), which may, relieve negative karma, accumulate merit, help rescue them from the sea of suffering and achieve Buddhahood. Speaking the mantra loud or silently, spinning prayer wheels with the mantra, and carving mantra into stones are the usual practices.
So what is the mantra? There is no definite answer to the question since it is not easy to translate the mantra into other languages. According to the Dalai Lama, the six-syllable mantra means one can transform one's impure body, speech and mind into those of a Buddha by following the path which is inseparable integrality of method and wisdom. The first syllable, Om, symbolize one's impure body, speech and mind, and also the pure noble body, speech and mind of a Buddha. Buddhism claims that an impure body, speech and mind can be transformed into pure ones of a Buddha, who was once impure and later by removing their negative attributes, achieved enlightenment on his path.
Mani, the jewel, symbolizes factors of method, compassion and love, the altruistic intention to become enlightened. "Just as a jewel is capable of removing poverty, so the altruistic mind of enlightenment is capable of removing the poverty, or difficulties, and of solitary peace. Similarly, just as a jewel fulfils the wishes of sentient beings, so the altruistic intention to become enlightened fulfils the wishes of sentient beings", the Dalai Lama says.
PADME means lotus and symbolizes wisdom. Growing out of mud but not being stained by mud, lotus indicates the quality of wisdom, which keeps you out of contradiction.
The last syllabus, Hum, means inseparability, symbolizes purity & can be achieved by the unity of method and wisdom.