I have the old Planetary Empires set for using in 40K campaigns, however, the set only contains random landscapes and Imperial ruins. For our dynamic campaigns, I am making simple faction specific tiles for some of the major armies.
Here is the first set of Necron tiles. This set includes a Megalithic Pyramid, a Tomb City, and a Plasma Generator. In our campaign, we are using the Mega-Pyramid as the Necron home tile granting reinforcement bonuses. The Plasma Generator boosts the points available to any nearby Necron forces, and the Tomb City is merely a thematic tile. Get creative and use them however you think is fitting!
Uncle Jesse's Gunmetal