Wow Andy! That oak tree is excellent! You could make a great weirwood tree for Game of Thrones along those lines.
That'd be REALLY cool!

I wish someone would!
Very nice paint on the GW castle, what's your recipe?
Now you have to follow this process correctly! It's all GW colours.
Undercoat the model in Black Spray.
Base colour is Zandri Dust.
Wash with a really diluted solution of Chaos Black.
Get pissed off when the wash looks too dark and uneven.
Cry a bit.
Dry brush back to a decent standard with Zandri Dust, then Rakarth Flesh, then Screaming Skull.
After that you just pick out certain bricks with glazes of XV-88 and Chaos Black.
Tanks chaps!