Sizes, framing, hanging heights and listing photos — written from measurements, not from adjectives.
Mat width and the frame size it produces is arithmetic before it is taste. 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. Pick the border, and the frame size is already decided.
Print sizes and aspect ratios: what matches what comes down to five families, not dozens of unique files. 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.
What belongs in an art print listing's photos is five images, each answering a different question. The order matters more than the count. The first image has to survive being cropped square. The one that actually sells the piece is the one that shows how big it is.
Listing a printable when there is nothing to photograph 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. A buyer of a digital print pays before seeing anything except the images you built and the description you wrote.