The thangka has been around for a very long time. The nomads of Tibet always had a thangka of there personal Diety, families as well always had an area with there families personal Diety. When there was a move the thangkas were rolled up and placed into tubes, then when settled they were removed and hung in a new altar space, they were always in a brocade frame with wooden dowels at the top and bottom, and they had a cover that would protect them from wear and tear, also from the eyes of the profane. They were designed to be an instant shrine, the brocade itself is the shrine and the decore of the brocade were offerings... The nomads of course were moving all the time, so they actually would have a special tent just for this purpouse. Also quickly noted, the Phurba was derived from a tent stake which was made to represent pinning down. Padmasambhava (Vajra Guru) is the one who made it famous with the Vajrakilaya practice. He also pinned down all the disrupting spirits with a phurba where the first Tibetan Monestary was built, turning them all to Dharma protectors.

Thangkas are painstakenly painted with immence detail to the iconography which are all teachings of how to reverse the mind. Every gesture, body placement, impliment, expression, plants, even color, all these are done with a specific purpouse that will stimulate and subdue, and lets not forget, set free. All these images speak directly to the subconsciouss mind, reminding us of what we already know, but sadly cannot or will not accept because of our delusions. So for many the thangkas are strictly ascetism, they are very pretty to look at, and they are! In this way they are designed to inspire one to practice and reflect on what the Diety is teaching. In the Hermetic science one takes a pen, nail, or something small for which to meditate on. You stare at your chosen object for a few minutes gathering all the detail of this item into memory, then you close your eyes and visualize it in your minds eye, not losing any of the detail, mind you. When you can hold this image for more than five minutes without losing any of the image then you move on to other levels which these visualisations are so important. The same thing is with the Thangka! You study every aspect of it, first with study and mantra recitation, then with visual meditaion and finally in the minds eye, and finally you become one in absolute with the diety. Since every diety has its purpouse the outcomes will be different, Bodhicitta (compassion) runs through all of them, and yes, they will all guide you back to enlightenment. Its a tedious task indeed as we are all lazy and would rather watch a movie or play on the pc than put our lives to good use, for the benefit of others no less! You can find lots more information on thangkas online of course, and or from your teacher. 

If you are intrested in a thangka I suggest the following two Ebay stores, "Tanayaart" and "Himalayan Mantra" both of these sellers are very sweet and will help you find a thangka that is right for you, and there prices are incredably reasonable, and the paintings are stunning! You can find these stores at my world page. Injoy!