Art and its placement is subjective. There are no rules.

The world will also not end if you put them up and then change your mind, move them around and have to make a few extra nail holes. Use the OOK picture hangers with the thin nails.

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The question is Where do you want to hang them?

At the top of the stairs so you see them from the top floor? Centered 57"-60" off the floor as you look across the stairway. Or stair step, side by side on the steps? Find the spot and center 57" - 60" from the step you are standing on.

IF you'd like them side by side on the landing, stand on the landing and measure. So you see them from the living room. Lots of options.

I’d get some Kraft paper and cut to size. Tape the two pieces in the different locations and also test height and proximity preferences. Also consider where they will best be appreciated.

On that wall facing the stairs 6097 and maybe paint that stair wall a color from the art .

You have a lot of wall space for artwork. Those 2 pics are just a start. Determine where you will place additional artwork and this might help with your current decision.