A toxic over-grown Industrial district in the jungle. Some arctic ruins bedecked in chaotic rites. And a coastal town that has some sort of undersea mining facility connected to it.
Civilian-styled urban areas. The grandois gothic architecture is all well and good, but I'm partial to contrast. Seeing CSMs, LSMs, Orks, and Eldar all fighting it out in an area that looks like it was made for normal day-to-day life would be an interesting scene.
I would also like to see a wide and varied range of biomes represented in EC, and while this is not strictly on topic, since the "option" of additional worlds was mentioned in the OP here once again is the math....
I'm with DJ on the Hive city theme. Deep striking into the heart of the enemy. Hearing the sounds of war erupting from every direction as Battle Brothers pour from pods all across the city.... Seeing huge, gaudy towers, gigantic statues, monuments... Hell yes! I think it would also be pretty sweet to fight through waves of mutated feral beasts at some overgrown ancient ruins with a 10 man squad. Then work our way down inside an ancient temple with as we descend into darkness looking for.......
Tyranid infested Space Hulk. I don't care if it's still drifting in space or half buried in the planet. Or Arizona. I nice wind sculpted rocky desert would be pretty. Considering there are two or three stars in the system, it's not too wild a wish!
I'd love to storm a bunch of space marines entrenched in an old abandoned Imperial trench defensive line that spans a pretty big distance. Like an Imperial version of the French Maginot Line that's fitted with old but operational defense guns and basilisks. God that would be exciting to attack as an ork.
