Framing isn’t limited by size. You can frame any unique-sized art, but the difficulty of doing so will increase with size. This is because both the weight and creation complexity of the frame will increase with size. And that’s where custom framing is more advantageous than ready-made frames.
With custom frame art, you have more freedom to size the frame to fit the artwork perfectly. You don’t need to cut corners by doing so, allowing you to keep the artwork completely intact.