I remembered seeing Lightoss do something like that as well, but when I looked at it, I didn't like how it had looked. I then decided to have a shot at this myself.
Sadly the stage is not animated, mainly due to the fact, I sort of forgot the settings I used to achieve the sunset.
EDIT: I've now added the layer of grass that goes in front of the characters.
Anyway, without further ado, here it is.
Stage Link: http://www.mediafire.com/?0numxjmy4yd
Feedback on MI appreciated.
Next stage due out soon!