Wow! I cannot believe no one has commented on the beauty yet! Let me just say, this is spectacular, especially with a difficult medium such as oils!
Vision: The overall look of the painting is very robust and well laid out. I do, however, think the sepia has overpowered a lot of the greens you wanted to use. The branches and trunks are also ever so slightly too lightly laid, and are more like a ghost of a shape rather than an obvious tree or bush. Of course, this might have been what you wanted (: One thing I want to point out is how well the water is done on the waterfall! This is difficult to do with watercolor and acrylic, so I can only imagine how much time and effort it took to create that kind of wispy fine water stream. Let alone the spectacular mist effects!
Originality: Lower marks on originality because though the waterfall is superbly done, the angle is quite overused, and a pronounced right or left angle would have really added to the depth. I do like that the rocks are highlighted in a way that I do not see often. More of a unique "crackle" effect that makes them pop out in the scene.
Technique: Even though you might have just wanted the trees in the background as a hint, they get lost from the similar toned blue/grey skies. A more pronounced structure would not take away from the waterfall, but instead add a little more composure it might otherwise be lacking. I can also say a bit more shading in the crevices and "rock wall" would be well used. I love contrast, so that just might be my preference.
Impact: I love the colors you chose for the rocks, their value is very subtle and warm, but the waterfall and the brilliant white complement it perfectly. Excellent job! ^^