Without any further delay:
That looks great! I have no crits, except that It would be cool to have a wallpaper sized version, but w/e, it’ still a great render.
Hmm… sky is a bit too featureless and the horizon is a little odd. The tree itself doesn’t seem as detailed as the rest of the scene, and since it’s the focal point, it throws everything off-balance a little. If I were to change anything it would be to perhaps give it some lower branches, and then perhaps shorten the height of the floating rock. Nice render 
Great work. Do you think you can make the tips of the grass more pointed? Currently they (particularly the ones up by the tree) are bit thick, and don’t look quite right.
All in all a great effort. This may seem pedantic, but I would like to see a little more definition of the edges of the island and chain area. Maybe increasing the amount of ‘glow’ from the lava? Also I notice that you have mist on. I am not in a position to experiment, but perhaps a bit of volumetric light from the lava might look good around the chains?
Anyway, better than I could post! Well done!
Ben