Here I've laid down some flat colors for the background. Everything is pretty much the same as before, but you'll notice that I added another tree in the foreground. The reason I did this was because there was a lot of dead space in the lower right corner. By adding the tree there it (as well as the tree behind it) helps to frame and lead the eye to the macaque.
I've cleaned up the coloring and painted the trees, which took a lot fiddly detail work. I also went in and added more elements to the samurai mask, since that's supposed to be the creature I'm designing. I give it a lot of tentacles that seem to be coming out of the fur of the macaque, suggesting that the macaque's inner body isn't quite what it seems. I've also given it some vestigial arms and legs to suggest that if it had to leave this macaque body behind it could very well do so. A lot of that detail is lost in the final image, so let's zoom in and take a look.
So this is actually a more updated version of the last image. I added some more detail to the mask to make it look like it's a hundred years old (referring to the Japanese legend that 100 year old inanimate objects will come to life). I also altered the mask's smile and its eyes somewhat so that it looks less crazy and more sinister. All of the eyeballs are now pointing in one direction, suggestion that it's found a target, and the mouth, instead of what earlier looked like a snarl, now seems to be smiling mischievously.
This is the final image I submitted to the challenge. You might notice that I cropped the image a little bit. I wanted to be able to focus more on the macaque than the surrounding background. While it cuts off a chunk of the background that I spent a lot of time working on, I think it was for the best since cropping like this eliminated a lot wasted space around the edges that could be too distracting to the viewer.
I really liked how this turned out, although I must confess to some bewilderment that it didn't get a lot of love from the people at conceptart.org. While I wasn't expecting to win the challenge, the fact that this piece, only garnered 1 vote and last week's got 5 votes confuses me, especially since I poured a lot of thought and time into this and last week's piece was almost a throwaway art exercise for me. Ah well, c'est la vie!