OMG! I found this picture on Google back in like 2011 and I've been looking for the original owner ever since. Now that I've found you I'd just like to say - this is freaking EPIC. No joke, I have literally never seen a better Avatar picture. You've got everything in here and it is all beautifully drawn (looks like it's from the original show) and I just love it.
I think it's interesting that while the fire and earth signs are on the left, Toph and Zuko are on the right, and while the air and water signs are on the right, Katara and Aang are on the left. I don't if that was by design, but I think it's really neat either way.