Here are the pictures.

And some more

Pottery Barn has a beautiful Bird Medallion Rug in blue that I could see in this space. I think I would find a beautiful, low bookcase for the entrance and hang a piece of art above it. You could still use the chair at the bottom of the stairs by the bookcase. I love the simplicity of the space.

I think it's the lack of color that makes it lack pizazz. I would rearrange hubby's sword collection around a colorful painting. It might be a period style painting of a soldier brandishing a sword, or whatever it is that they do with swords. Well, okay, you said we couldn't move the swords, so I retract that suggestion. Instead you could put the sword painting on the stairway wall, going up the steps, or elsewhere. A bench under the swords would look nice.

I do see bare walls in your photos. Photo 1 has a painting (?) hung rather high on a wall, while other walls have small framed items at odd heights. It could be more interesting to group all those things together on one wall as is shown below.

How about painting the whole area a color? So what if hubby is color blind. If he's red/green color blind, he probably likes yellows and blues because he can see them.

Lighting might be a problem. Adding a couple of wall sconces should be pretty easy, and could create a feeling of coziness at night.
Carolyn Albert-Kincl, ASID