better photos of the kitchen, please.

I would find a better spot for your prized art away from glaring light.

I don't think you need anything in that corner. Just have the art. It looks like maybe it's too high but hard to tell. The center should be around 60-62" high.

What I notice the most in your pictures is how yellowed your chairs look in your white kitchen. Perhaps they can be painted.

Definitely not a chair. Try a rolling shelf/serving cart or something similar that matches the style of your postage stamp.

Nothing is needed, and any furniture there is likely to make the space look cluttered or crowded. Check the height of your poster, as @justcallmepool noted. If it's centered at the correct height and the space still looks too empty to you, fill more of the vertical space with art. A second poster, or a long narrow artwork, a row of plates, etc.

Here's something similar, only the right size. Or really move the postage stamp to another place...

A low light plant with a plant light nestled inside the planter

Agree the print looks a bit high. Center should be 57-60” from the floor. I like Beverly’s suggestion.

If possible, a slightly larger frame could work. A narrow mat could be nice to enhance the print. This one’s very large but shows what I mean.

There is not enough room there for any furniture. I agree the art looks too high but could just be the picture. I like the above suggestion of making it a bit larger with new frame and mat.

I agree I don’t think you need anything more there. You could make the poster have a bit more impact by reframing and matting it especially if it’s something you really like. It’s worth the expense although Michael’s likely has a very standard frame that would work with this.

IKEA has a good selection of frames designed for posters that include the mat.