Forest Live Wallpaper is a nice, relaxing wallpaper with trees blowing in the wind and a sky that changes from dusk till dawn.
Don't forget to go into settings to turn on things like weather, multisampling* or the 3D parallax effect*, if you don't wanna miss out!
* Not supported on all devices.
How do I use this wallpaper on my lock screen?
You need to have a lock screen that can use live wallpapers as background, like Locker Master or something. The one in the screen shot is part of the ROM CyanogenMod.
There's a color setting called Night-time multiplier that you can change to a brighter color, making the trees and hills brighter at night. It's not the perfect solution, but it'll have to do until I (eventually) add a fix.
Make sure you have a location set in the location settings, then check if Recent weather data (via the menu in the weather settings) is available, up to date and for the correct location. If not, the weather provider is simply not accurate, but now you can change the weather provider.