With dozens of both Mahayana, Vajrayana monasteries and to the east Theravadin monasteries Lumbini has plenty to choose from. This Tibetan Temple contains one of the more colorful interiors.
Photography is often banned inside monasteries and temples around Lumbini so be sure to ask first. While security is not always tight there are always plenty of people around.
Read more about this area in the Lumbini guide or check out this photograph of Buddha in Tibet.