All of our rectangular canvases are both landscape (horizontal) and portrait (vertical) as the hanging devices are placed on both - the short and the long side.
The only important thing is to make sure the image is uploaded with correct orientation to ensure a good position of the hanging devices.
To do so, an image for canvas wraps should always be uploaded with the top facing up or to the left. This way the devices will be placed on the top of the image regardless of it being a landscape or a portrait.
If you have any questions about this, please feel free to reach out to our friendly support team!