The "Star of David" on the shields and military standards is inaccurate. The symbol only came into common usage as a religious/national symbol many decades later. (Some believe during the middle ages)
Assuming that this symbol represents David, as the name suggests, this would not be an Israelite symbol until the time of David's Kingship. This is out of place during the reign of King Saul.
Shown in the confrontation with Goliath, David using a sling strikes Goliath on the bridge of the nose and the rock glances off. According to the Bible, David struck Goliath on his forehead and the stone sank into his forehead and Goliath fell on his face to the ground. (1 Sam. 17:49)