Okay so Calactyte, I was going to bring this up later but seeing as you're going to send the Pit to Interloko soon, I should probably do it now. This post is more about functionality than aesthetics.
So firstly, I'm assuming that the shadows in the middle of your bridge are from the clouds overhead. However on the off chance that they're not, they shouldn't be there since the backdrop of the moon and mountains is supposed to be a fixed image, so the moon should be casting light on the bridge at all times. Apart from cloud shadows, there should be no variations in lighting.
Here's a little breakdown of the Pit:
* The bridge/yellow background represents the length of the stage
* The Pit backdrop represents the area where both characters start, this one is formatted to 16:9 already
* The clouds here are the total amount of clouds that pass the screen, this is their exact positioning at the first frame
For the sake of accuracy, your backdrop should be similar to this 16:9 image (ignore the leftmost side of the mountain as I've just mirrored it to extend its length):
I still feel the mountains in your backdrop need to be replaced, as to my eyes they are clearly lower resolution than everything else. But after that backdrop is finalized, anyone else who is working on the Warrior Shrine, or Test Your Might, should use it because the one that is in the Pit is also in those stages. Otherwise there could be some obvious inconsistencies in the backgrounds.
Another issue is the height of the stage. The height between the bridge and the bottom of the stage doesn't matter, since it's only function is the distance that the character falls. However, the height between the top of the screen and the bridge does matter, and its something that should be amended in your version.
Here is Interloko's rip of the stage:
Here is your stage resized to the width of Interloko's, and moved up to match the position of the bridge on the screen:
As you can see, the backdrop is up too high, cutting the moon off. Since we've agreed that the characters need to have the same distance in height from their heads to the top of the screen as the original, the way I've composed it here is the way we've agreed on. So it's necessary for the backdrop to be moved down. As for the situation when characters jump or are uppercutted, the stage lifts like so:
The backdrop is still in a fixed position of course and so there is no additional space above the moon. I'm not sure whether you're in charge of making the final compositions though, so if you've left that up to Interloko then I'm sorry for wasting your time with this.
Lastly onto the clouds...
Your most recent version of the clouds looks good and fits with the stage. However if you wanted to get it really close to the original, its the animation, size and positioning that would definitely sell it. I'm not sure if you have started on the animation yet or if you are even doing it, but I've composed and calculated this, and it wouldn't be hard to do. Here's the reference image I've made:
This is the total amount of clouds present in the stage. They are made up of 3 rows that each move at different speeds to each other. I've worked out the duration of each row, in regards to how long it takes for them to pass through the stage before they loop:
Top clouds: 21s
Mid clouds: 28s
Bottom clouds: 42s
You can refer to the first image in this post for their exact positioning on the screen from the first frame.
Anyway all that would be needed is roughly the same amount of clouds, and three rows with each one being of similar size to the original. They clouds don't need to look like the original, what you have is good is at is, but IMO it'd be better if they occupied the same amount of space and behaved the same way.
So that's all for now, please consider what I've written since any changes should be easy to implement and would be beneficial for the stage IMO.