My suggestion is to find objects/art you like. Then arrange them as needed. Don't race out and buy cheap pictures in cheap frames and hope they make your space look great. Not that cheap is a bad thing, just try to not fill the walls with too many items. Negative space adds value!

I have a fair amount of art that I collected over the years, some expensive and some not. But every time I visited a friend, who studied and worked in the art field, I always felt I didn't have much art. Her home was filled with art on every wall, from the floor to the ceiling. It worked in her house and was an amazing collection to look at. I could never live with that much art on the walls.

All that to say, that each person will have their own perception of what is too little or too much when it comes to art in their house.

But Gary is correct, do not go out and buy stuff just for the sake of filling up walls. Take your time and get things you like, better still, things you love.

Also don't be afraid to move pieces around. Because you put a nail in the wall doesn't mean it has to stay there forever. Nail holes can be easily touched up, specially when you have leftover paint.

It’s hard to tell what’s going on with your lighting in the stairway since the last picture is so much brighter. Where is it coming from? What is the round hole above the light fixture. I don’t think that bright circle on the wall is what you want with art work. Is there a ceiling fixture?

I agree add art when you find a piece that cries out to come home with you. We have collected art for the last 30 yrs and we make it a rule to meet the artist it just makes the whole experience a bit more fun. I do not like family pics hung in public spaces so hallways are great spots for them . If you lean towards contemporary I would suggest all black frames in one size with different sized matts and hung in a row like in a gallery.