The most original thing I found about the character and creature designs was the hair sex for the Na'vi (should be considered the most impractical reproduction system, ever). Just the thought of all the possibilities regarding this idea makes me giggle inside. So many jokes... XD
One thing I can say about the plot that I did enjoy was the parts regarding the function of the avatars themselves and the technical aspects that made it possible for the humans to live on the planet (not being able to breathe the air on another planet, while not original, did help provide some decent suspense when it came into play). I would not have minded the movie too much if it did not recycle so much of the formula while at the same time creating issues with the plot because of said formula. Not to mention that I disliked similar movies like Pocahontas because of the plot, so it was doomed for me at the very start.