You guys, those edits are great in all, but are adding a new issue now: the leaves of the trees, especially starting from Indigo's edit, are pushing them to the foreground now. If the leaves of the trees are active bushes that once hit, give you some extra goodies, like health, 1 up, or mushroom(heh), then it's fine. However, 2 hues of the leaves of the trees in the background, are about as strong/vibrant as the green in the ground tiles. I was under the impression that further back is usually less detailed than things up close...don't know but I could be wrong. And Adar dar, I guess that's true, but I'm sure there have been several games that make this mistake as well, so maybe it's not as big an issue as it would seem. Here's a less than great edit from yours truly:
I took out the background tiles, but that isn't to say that it looks fine without any. This is just so you can focus on the trees and how they can blend into the background without having other distractions in the piece. The background tiles are ok, but maybe you should try experimenting with some different types of tiles, like distant trees, with minimal light coming through. That, or change the background tiles so they don't read so much as squares, that punch through the dark bushes...or a different palette, or some junk.
Btw, I still think this is some solid ShriT right here. Please keep it up...