Obsidian has confirmed that tilesets will only be used in in-door areas. Outside areas will use height mapping.
“This tileset is used for the dead....or undead. It can be tinted but has no meta tiles. This...Crypt tileset
“A tileset is a collection of tiles which follow a common theme. They allow module creators to...Tileset
“This tileset is used for most indoor structures like townhouses, taverns, and shops. This...Standard Interior tileset
“No adventure game would be complete without dark caverns containing all manners of scary...Caves tileset
“This tileset is used for mineshaft areas, but unlike NWN1 is a separate tileset from caverns...Standard Mine tileset
“This tileset is used for the ruins of the Illefarn Empire, featuring ornately decorated...Illefarn tileset
“This tileset is used for the last dungeon of the official campaign, featuring dark stonework...Shadow Fortress tileset