I've seen this concept art related to Avatar movie several, times but for some reason I've dismissed it as fan art, and never paid much attention to it. Eventually I was able to find such an image with the Weta watermark, which raised it to official status. But I still dismissed it as a abandoned concept, since the Na'vi Language page tells us that they have no written language.
But in my latest re-watch of Avatar, I noticed this concept image inside the Old School House. As shown on the right image. Does this mean that the Na'vi have some kind of rudimentary symbol system (pictographs) predating the writing system?
Markings on the Weta rendering of the Eytukan bow. Markings on a war axe from Project 880 days. And marking on the Staff of Wii game.
Worth noting is the the Wii game uses in-development resources, most noticeable from the way Grace's Avatar looks. So that may indicate that in some point the Na'vi were supposed to have some sort of writing system.