I decided to go with a warm reds on the base to make the cooler white and green of the Deathwing stand out a bit. The base is a bunch of Gale Force 9 snow mixed in with super glue, and a chunk of building from one of the Imperial Buildings. I kept the red on the building as well, as I'm trying to keep with the theme. If the earth is red, the building materials from the buildings should be reddish too.
Here's a biker. I gave him white highlights because I really like extreme highlighting. It may not be the most subtle or realistic method, but I like how it looks. The bottom edges of the bike where lightly drybrushed the same red/brown color of the base.
A wash of some sort of light blue will is probably heading straight for the white angel wings on the bike.
Anyway, this week will likely see the completion of a squad of wracks, and their raider, after I refine the Green Stuff work on it.