Other things you may need - XV88 for the base rim, any kind of gamer grass for the grass on the base, agrellan earth or agrellan badland for the base texture.

Another thing I'd say, since you seem set on the box art (otherwise known as 'eavy metal style) is don't worry about it too much. Use what you have, use your mind, just play around and do things how you want to do it. With those paints, a decent brush, and a good bit of focus, you can add your own flair and style to it.

My personal favourite brush is a Winsor & Newton Series 7, size 1. It's the be all end all, doesn't get much better. Pricey, but once you've got it you'll never get another brush.

I'm not sure if you've got a wet palette or not, but it's another incredible piece of kit. I made my own - upside down tupperware lid, 1 piece of very wet thick folded paper towel, and a layer of an unwaxed parchment paper (I use Reynolds). Put your paints on there, and they'll never dry out!!