well, we each have our own ways to express our own devotion to the deities. Some Tibetans like to put all their statues onto a single platform. Somewhat like a happy family playground. Others prefer to be simple and put just one statue of Buddha to represent the entire merit field. Either way, it does not deviate from the Buddhist tradition of generosity and making offerings.
From the pictures of this altar, we could also tell that the Buddhas have no sense of differentiation(heck, they have attained the siddhi of equality!) There is no such thing as this Buddha is above than the other and hence when we are attained, being in the front or later makes no difference already. Its our perceptions that entrap ourselves in Samsara