Here are photos. I thought it would look great, but it really looks stark and too small to me. Any suggestions? Thank you!

Have it set into a frame with a large matt around the perimeter and narrow matting between each panel. You could then place smaller artwork or candle sconces to either side of it.

I should also mention that they are made of sheet metal and made to be hung directly on the wall without frames. There are holes in each corner for them to be nailed into the wall. So I don't think framing them would work.

Possibly space farther apart and mount them onto something else larger and darker and then hang. That might be very "custom" and actually define the images even more dramatically. They look a little pale against the wall.

Here's an example of adding more to the wall to balance it out
http://houzz.com/photos/16307960

I can't really see what the triptych is but it's not at all too small. It should be slightly less than the width of the furniture beneath it and this looks close to the width of the furniture. The size is just fine. By the way, I LOVE your paint color. It's beautiful with your dark furniture. I might decorate the top of that furniture piece in a different way. Maybe something like a single large oblong bowl and no pictures.

If you happen to have two spare dining chairs, I might place one at each end of that furniture.