[llamabeast]

You should probably aim to represent ground combat on the surface of a planet. Perhaps the planet is strategically crucial or something. Games like Dawn of War tend to go with that kind of concept.

You could certainly have close combat troops (there are plenty of examples from sci-fi, e.g. Jedis, zerglings, aliens from Alien etc), plus obviously ranged troops. They could be tricky due to the lack of appropriate projectiles. Of course, for real laser weapons no projectile would be visible. Still, it would look strange not having one.

I think this will be hard. Probably you should start with just two races. Maybe something really coolly thematically opposed, a la Terrans/Zerg or Space Marines/Tyranids.

Spells would be interesting. I wonder what they would represent.