what size is the stairwell? 3' Wide x 9' long?

12" diameter fixture.

If that’s the norm and I have an 8” diameter by 36” long fixture, will it look bad?

I had a very similar dilemma some years ago with a two-story basement stairwell that looks a lot like yours. I finally decided to get a hanging light with three arms and three bulbs. It's about 15 in wide and hangs on a chain. I couldn't figure out a good way to photograph the stairwell due to the position of the door. But this area tended to be dark and the three light fixture was perfect to brighten up the space. So I suggest you think big on this one.

I switched to the same pendant at 16” diameter and 46” total length. The distance from stair to junction box is 14’. Standing at the top of the stairs, that is at my chest.

Sound right?

Commercial Electric Flexinstall LED 14 in. White Disklight Flush Mount Recessed Light

I would use recessed lighting or a thin flushmount like^^.

A basement stairway generally doesn't merit having anything decorative. Utilitarian is fine, IMO. And I wouldn't want something fancy that needed dusting & cleaning over the stairwell. Not worth risking breaking your neck over.

ETA: The single pendant will underscore how tall and skinny the space is. Not something I would want.

This is a basement... as in utility and storage? Then no shadows please.

Went with this at 16” wide and 46” long pretty and utilitarian-ish

ItIt’s a finished basement with carpet. Family/TV room

I like the look of this but I’m unsure if the bare bulb would be glaring.

It may be best to also light the stairs. This is from engineeringdiscoveries.com.

Oooh. That’s cool. Historic home, though.

If people 100 years ago had a choice to be safer walking down into a dark basement they sure wouldn't have been concerned about style or history.