What Is It?
A Triptych (pronounced Trip’tik – did you get it right the first time) is as one would think involves three of something. In photography (and painting) it’s often referred by as three-panel wall art. There are no stead fast rules as it’s art.
The Triptych is preceded by a Diptych and followed by a Quadtych, Polyptych which leads to what we know as a Collage.
Two of Many Paths to Take
1) Use a single-image split into three panels image in portrait or landscape position with framing, shadows… added for desired effects.
2) Take three similar / closely associated images into a single three-panel image in portrait or landscape orientation with effects added to taste.
At this moment, I like the single image Triptych best.