I just put together a mod that adds the skies from Kingdoms into M2TW.
DOWNLOAD LINK
To install, extract the contents of the .zip into your M2TW data folder, and make sure you are using the IO file_first switch. If you want to use this with a mod, extract the zip into the mod's data folder. It should be compatible with any mod that does not change the weather, skies or any of the files included in the download (expanded.txt.strings.bin, weather_db.xml and all the files in the globallighting folder).
This mod does not change the weather you will get in your game, it only changes the background skies. All the original skies can still be seen, but half the time the game will use the new skies from Kingdoms.
This mod does not change skies in the winter season, because I do not have winter in my game. I released a mod that removes winter from the game, which you can find here.