I am considering basing my mirror army with charred grass and ash, and make the important figures stand out by putting them on slate, as well as what I just said. Is this a good idea?

This is exactly what I wanted to do.

Sounds good, maybe do a couple of test bases first if you're not sure. That way you can always change your mind if needed.

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Soon Master Elf, you will enjoy the fabled hospitality of the Dwarves! Roaring fires, malt beer, red meat off the bone!

Will try that soon!

I'd recommend checking out Vallejo's texture paints. GW makes some too but Vallejo's are much, much cheaper. Anyway, the line is near the bottom of this page http://www.acrylicosvallejo.com/en_US/d ... /family/35 and I thin that the Black Lava-Asphalt would be great if you wanted to go with something more volcanic and Dark Earth better for a dark/dead but less volcanic look.

It's really great stuff, I've got quite a few tubs and love them.