The Buddha Maitreya, after the conclusion of the current period dominated by the historical Buddha Shakyamuni, will come to earth as the last earthly Buddha. Until the time of his appearance as a Buddha, Maitreya resides in the Tushita Heaven as a bodhisattva. According to Mahayana teachings, a Buddha is first born as a bodhisattva, and then after many lifetimes, progresses on to Buddhahood. The historical Buddha was himself referred to as a bodhisattva before becoming the Buddha. The Buddha Maitreya, or Bodhisattva, is here represented as princely figure, alluding to the historical Buddha’s life as a prince before he renounced his kingdom. Bodhisattvas are indeed more richly attired, compared than other figures of Buddhas which appear attired as mendicant monks.
To find out more about Gandharan art please see our relevant blog post: The Influence of Greek Art on Gandharan Statues.