You can post your images to 750pixel on the long side to make it bigger. Judging from the smaller image, I like the composition. The large standing trees and falling tree in the water contrast nicely with the smaller group of trees in the BG left. You also have a nice "V" in the water leading ones eye from the FG to the BG. I am not sure about having the horizon in the center of the image but it is not really bottering me here. I think the other elements in the image balance it out nicely.
You could try taking some of the top, or bottom and seeing how that looks but I like it as is. I would have preferred to see the top of that one tree in the upper left not cropped off. I can't judge tonal relationships well with the smaller image. You are welcome to repost a larger version.