You may already have seen HBO's cool new promotion for the show at www.JointheRealm.com, where you can create your own House Sigil, like the Starks and the Lannisters. Warning: it's addictive!
My first stab looked like this - based on Berry's Second Law (per my father) which is the motto:
The dragon and the unicorn face outward, as if searching, each symbolizing a different aspect of love.
Berry's First Law is: "When in Doubt, Go Left," which would also make a good motto, seems to me.
Then my best friend told me no, obviously my motto is:
Yes, it's a line from the movie version of Fellowship of the Ring, spoken by Galadriel. As soon as he saw her get all glowy and crazy when she was tempted by the ring, my best friend pointed at me and said - "That's you."
The symbol is a phoenix because it just looked right to me - kind of like Galadriel with her arms out, radiating power, immortal, death/birth.
One's friends give one an interesting perspective on one. Don't they?
Yes, I love the color green, so I keep using it. Maybe the "All Shall Love Me" sigil should be black or red, with a skull or something.
Or perhaps to show we don't take it all quite so seriously:
What's your sigil?