Scenes

Snorri:

Camera Instance

Use Show Display to instanly see the camera's view (with Render Skybox on).

Siege Engines

Snorri - from extensive siege scenes testing from creating them and figguring out how to make AI stupidnes at leest mimic what should be done

Siege engines mostly aim for enemy siege engines (or rather siege engine crew), so anything around them could also by targeted by mistake. Placing your troops next to siege engines is not a best idea.
It seems that after extensive, non effectice fire to enemy siege engines, or if they go beyond reach, or if there any from start, it choose another target.
Siege engines can aim into singular troops, and it's super weird how precise it could be. Usually they will chose targets that are closer to them, but not always, it dose't seems to me that AI know if it shoot to whole formation or singular troop, so it will not chose to shoot to bigger stack as would be logical for most kills ratio.
Siege engines need more or less direct sight to target, they can't shoot over walls, hills etc. it also don't care if friendly troops are in a way, that's why most defender siege engines are places nearly always so much on front, they can do sooo much friendly fire if you will give them a chance (as they will chose to shot more nearby enemy that is probably in fight with your troops).
Siege engines don't seems to care about destructible things as merlons and roofs, they destroy them by mistake trying to target troops/siege engines.

It's all from just extensive observations and testing by changing things in scene editor.

Various

search for "debug" in the entity browser, place it down and run it's script, there you can choose what type of scene you are making and see the requirements for it in terms of spawners and such

Native scenes with terrain

FoozleMcDoozle:

The only base game scenes that have terrain are:

sp:
empire_village_003
khuzait_village_g
battania_village_k
sturgia_village_l
khuzait_castle_002
sturgia_town_b
battle_terrain_v
empire_castle_keep_a_l3_interior
empire_house_c_tavern_a
empire_dungeon_a
arena_empire_a
Main_map
sea_bandit_a
mountain_hideout_002

mp:
mp_siege_map_003
mp_skirmish_map_002f
mp_sergeant_map_008
mp_tdm_map_001
mp_battle_map_002
mp_duel_mode_map_004