You forgot 'Badass Beauty'.Now that Clarion Call is out I'm wondering about the significance of this even more. Possible ideas:
1. A Wedding rune.
2. Symbol of Utena Tenjou, Goddess of Beautiful Badassness, Epic Victories, and All around Awesomeness
3. Rune for Corwin/Anthy's child.
4. Odin's Wife's blessing rune for both Corwin & Utena (loved her speech)
5. Corwin's Rune (once he finally displays his) - as it looks somewhat like a symbol from circuitry, and would be rather fitting considering his 'realm'.