If it's in the budget, adding light fixtures in the hallways would really improve the lighting and make it less gloomy. I would move the art from the left of the window to the right.

Apart from that, what is the space usually used for? Is it mainly a transition to little-used spaces like storage or guest rooms? Could you envision people enjoying a little game table or reading corner there?

To the left is the entertainment tv room and to the right is a bedroom.
My laundry room is abutted next to stairs.
This area has heavy traffic.

The laundry room is to the immediate left side.

Sorry, laundry room to the immediate right side.
The immediate left is a broom closet.

I wouldn't really add any furniture there if it's a heavy traffic area. New lighting would help, but if you want to make it more fun a rug would be your best bet

I was wondering about improving the appearance of the wall space.
Mirrors? Canvas? Metal art?
Narrow Sculptures ?
I would like a FUN COOL factor there as a focal point coming down the stairs.
I gravitate toward contemporary/ modern style.

Make a statement with a small gallery wall of round mirrors! And if there is room add a narrow console table underneath the mirrors.

Make sure to scale the mirrors to your space but here is another idea!

I like the contemporary mirror idea or bold large canvases and a super narrow console might work. Should I go with lighter color wall on that entire length of wall and also the sections of wall directly in front to the right and left?
The entire downstairs and the stairs area is of this same color.
Would it look disconnected?

I would change the color of just that wall to a light muted color with a gray undertone. What colors do you like?

Sherwin Williams Misty 6232

Sherwin Williams Modern Gray 7632

Sherwin Williams Zurich White 7626

Here are some wall color ideas.

I think the biggest factor is adding light to the room, possibly recessed cans. Add some simple artwork. Depending on your style, we lean to neutral paint colors, but if you like warm colors I wouldn't worry about painting. Unless its been ten years since painted... It looks like you have low ceilings, so the more items your have in a room the smaller it will be. I personally would add a small table with one or two decorative items on it and perhaps the mirrors above. Create a focal point and help balance the room. I would keep it simple.

Definitely definitely add can lights to the hallways. It will help so much. You could think about possibly moving the light switches for the tv room and guest room out to the hall too, so you can turn on the lights before you begin the journey down that hall! I hate to be negative about someone else's home but for myself, I would have to work up great courage to walk up to that gaping black hole and reach my hand in to turn on the light. Not everyone is scared of the dark though.

The mirror idea is good :)

You could use LED wall sconces for lighting!

Improved lighting and a console/art/mirror would def. help. I also find the carpet a little glum in combination with the walls. Perhaps a hardwood floor with a colourful (non skid) rug might help? If wood is not an option, cork is a great alternative and can be installed on a slab if that is the case. Also, as it is a non public family area, maybe this would be a great place for a quality framed family photo gallery or kid art display. Here are a few pix for inspiration (love the blue piano wall!) Also, I am guessing this is a basement or lower level, I have found that installing a few "grow" lights (for plants) or full spectrum lights which mimic natural sunlight can help with banishing the underground blues.

I say more lights & your choice of wall decal

Here is a different idea. First I would find a small console table that you like, cut it in half (or less) and mount it to the wall.

Then I would do a white empty picture frame wall. Using frames on your window and other box as well. That way they are part of the decor instead of trying to draw your eye away from them.

You can use modern frames if you do not like the vintage ones. Or frames only, and no console table.