Animated 2D images

So, I got that idea stuck in my head...  I really like slightly animated 2D images, or short films made with that kind of technique. So seeing the short series for the warlords of draenor finally pushed me to delve more into it.
For an easy start I wanted to learn how to use particle effects in Adobe AfterEffects for admospheric effect. For that, I used this little scetch

And here's the first draft for the animation

At that point, I'm quite happy with how the rain and fog turned out, but there's still room for improvment!
Next step will be to add a nice, gloomy glow effect and movement to branches and details on the mantle.
After that and if everything works in the demo, I'll finish up the drawing to make a fully fledged animated still out of that :)