I would stack them.

Even stacked they are still out of scale. If you like them, which I do, find another home and go with something different in that spot!

You think it will be still too small stacked?

Even if they fill that slice of wall you have a lot of grey wall around them. It's not just about filling the wall but filling the space. Though it is hard to say from the photos.

It's not scientific but have someone hold them up in the space and take a step back. If you like it hang it!

I'm not a pro so maybe my opinion doesn't matter, but I love the picture in that space. I think stacked could work well, but I also like the single right there. For me, I like having some wall space around art rather than trying to fill up the space. Plus if you love the art, that's really the most important part in my opinion.

Think you pricklypearcactus! I just think it looks a little lonely on that wall:). But I put the other one in a little nook and I love it there so I’d rather not move it!:)

To me the issue is, unless you live in a beach house which it doesn't look like you do, the content of that art doesn't make any sense. To me it looks like coral (?) Even if it's not coral and maybe it's a shrub, it still doesn't make any sense to put pictures of shrubs in a hallway. I don't mind the scale so much if they were stacked, but to me there is no reason for those pictures to be hanging there. Find something that is not only more visually interesting but more appropriate for a hall way.

Purchase one more, stack and put the odd one in-between the matching two. Or buy the mirror and stack with mirror.

Try two or three stacked. Here are some images to help:

Modern Luxury Home · More Info

Beach House · More Info

Inman Park Bungalow · More Info