Avatar is a weird franchise (yes, franchise even though none of the follow-up movies have come out yet), because people became obsessed with the world of Pandora. I don't know why. It just seemed like a normal jungle but made out of CGI. "But everyone lived in harmony. It's beautiful." That's not true. The main character was almost killed by deadly animals in Pandora, and the whole place was easily destroyed and brought to war. Not the greatest place if you ask me.
People who love Avatar will go beyond just cosplaying as the characters. They actually want to live as the creatures. That's why I'm not too sure if this is cosplay or someone who never got a date in highschool so now they pretend they are from an imaginary world. We all cope in our own ways.