Here is an excerpt from a talk given by the Gyalwang Karmapa in Bodhgaya in 2009 where he discussed the tormas:
“Also, we have expanded a number of the features of the site where we are holding the twenty-sixth Kagyu Monlam, including the main gates and so forth, and I thought it would be good to briefly point out what the tormas represent. The main decorative tormas are those with images of Marpa, Milarepa, and Gampopa on the right, and on the left, those with images of the forebears of the Nyingma school of the early translations, the glorious Sakya lineage, and the Gelukpa order.
The main principle these tormas illustrate is that when we consider the Tibetan Buddhist teachings, there are basically no lineages that are not mixed with the others. When the three Dharma kings Songsten Gampo, Trisong Deutsen, and Tri Ralpachen first established the Dharma in Tibet, the lineage that emerged at that time became known as the “Nyingma school of secret mantra.” Thus the Nyingma was Tibet’s first Buddhist lineage. Later on, during the reign of King Langdarma, the teachings were wiped out of Tibet, and the later propagation of the teachings began. That is the difference between the Nyingma and Sarma vajrayana schools.
Then the oral lineage of the Kadampa masters was passed down from the glorious Atisha, and the Sakya, Kagyu, and Geluk lineages successively appeared. The stages of the teachings of all of these lineages, along with their basic starting points, are the same. The different individual lineages arose out of different lineages of lamas and instructions, but fundamentally there is not even a single lineage that is not mixed with the others. In sum, all Tibetan lineages have been passed down intermingled with the others—all of them share Dharma connections and connections of samaya….”
“Therefore the presence of images of the root and lineage gurus from all of the Tibetan Buddhist lineages here today means that all Tibetan Buddhist lineages are nothing other than the teachings of the Buddha: They are all the same….”
For the entire teaching see link below:
A Talk on the Relationship between Masters and Disciples
January 04, 2009, By 17th Gyalwang Karmapa
Translated by Tyler Dewar, Karma Choephel, and Ven. Lhundup Damchö for Monlam English Translation Network.