Hugin and Mugin

Digged into Norse mythology and man.. I love it!
Here two ravens - Hugin and Mugin [hugging and mugging? hmm ;) ] - which Odin kept sending to soar across the lands for him. Once they returned at day's end, he'd listened to what they had spied upon and discovered on their journeys.
Aand that lovely symbol placed in the middle is called 'the Valknut' [ from Old Norse valr, 'slain warriors' and knut, 'knot'] which is often associated with Odin; there's no clear explanation on what exactly it stands for, though.