
This is one of the decorative mandorlas painted behind the remains of the Buddha statues along the east wall of Cave 2.
The petal-shaped nimbus is decorated with blue and red curves on the inner edge, and the outer edge has a yellow flame pattern. The mandorla has multiple layers of color, and the outer edge consists of a yellow flame pattern. This style of mandorla was popular in Tibetan art during the 10th and 11th centuries, and can be seen in the images at Gyangbu Monastery, Yemar Monastery, Dratang Monastery, and Jokhang Temple.
For more details, go to the Encyclopedia of Buddhist Arts: Caves A-E, page 325.