Hills need to be visually distinct from plains. (For movement)

Forests and swamps need to be visually distinct from plains. (for movement)

Swamps need to not look like forests. (for city placement)

The terrain for quest locations needs to not look like a different terrain type. Don't have a forest background if it has appeared on a plains. Either just spawn the quest locations on appropriate terrain, or have them visually adapt to the terrain that they spawn on.

It feels bad trying to move across a piece of plains only to discover later that it is something else.

It feels bad having built a city, and trying to work out why one cannot make lumber improvements, only to discover that the nearby forest is actually a swamp.