Nice image, just a few ideas Instead of blurring that part of the mountain maybe use some low lying clouds or even try get hold of another image with mountains in the background, you could then keep the foreground of this image. When doing hair its hard, we all go through it but if you use the lasso tool etc you can adjust the feathering Took me a long time to catch on to that one. Lastly is the skull in question, it still looks like its floating on the background, it might be because of the bluring in the rest of the image, makes the different textures stand out. But hey, you have a week to play with it. Goodluck

The skull pieces need some grass blades in front of them so they don't look like they're floating. Try using the smudge tool at a very small brush size around 75% strength or less.

Nice idea. The smudge tool is your friend!