I like a fairly bright universal lighting and a lighter shadow effect because it's easier to see the objects in the rooms.
However, some people love dark and barely visible.

One idea for the wall shadows is to have two levels of shadow.
First, a darker one on the floors, like you currently have.
Second, a thinner and lighter shadow above the furnishings to still provide a slight shadow effect for items that are against the walls.

About the stairs. One convention is that stairs become lighter as they rise to the next level and darker as they descend to the level below.
The other convention is to have uniformly lighting on the stairs and to use the step shadows to show the up/down direction. That works, but often the direction isn't obvious at a quick glance.