Sizes, framing, hanging heights and listing photos — written from measurements, not from adjectives.
A mat is not decoration. It is the layer that absorbs the difference between the shape of a print and the shape of a frame, and its width is arithmetic before it is taste: pick the border, and the frame size is already decided.
There are dozens of print sizes and only five ratios worth knowing. Sizes inside one ratio are the same file scaled; sizes across two ratios are different files, and treating them as one is where white bands and cropped signatures come from.
Five photos, each answering a different question. The order matters more than the count: the first image has to survive being cropped square, and the one that actually sells the piece is the one that shows how big it is.
A buyer of a digital print pays before seeing anything except the images you built and the description you wrote. That puts two jobs on the gallery that a physical listing splits with the object itself: proving what the file is, and proving how large it will read on a wall.
The app does the same thing with a lot more room to work in, and it exports at full resolution.