The lover sets the banner of love over his beloved (2:4), and then the bride declares that her lover is a banner prominent among ten thousand (5:10).  Both use military imagery; the banner is a military standard.

But then the imagery works the other way, and the bride is bannered: as awesome as bannered ones” (6:4).  The bride shares in all that her lover has, and if he is a conqueror so is she.

Allegorize as you will.