Malbim: The flag of Yehudah had the form of a lion. There were 12 Avos from Shlomo until Yehudah, or from David until Yakov. Just like the Yam stood on 12 cattle, and the face of an ox was on the left, so Shlomo's throne of judgment stood on 12 lions, which are on the right of the [Chayos under Hashem's] Merkavah (Yechezkel 1:10), to include Chesed (which is associated with the right) in judgment.