Does anyone know what the actual requirements for a scrivener corkboard background are?

Does anyone know what the actual requirements for a scrivener corkboard background are?
I have such a hard time finding images that won’t tile or only show a tiny corner. What is the magic formula for an image that will work? I like to change it up for every project, or sometimes just as a way to refresh my creative mind.
Can anyone offer a solid answer that will make these easier to find and/or create?

can either use small repeatable tiles/seamless to create uniform background, I have some 300 by 300, vs large picture which has be be at least 1400 to 1500 pixels by 1000. this is on 27 inch monitor may be different on smaller screen. Lots of nice small repeatable tiles on line or could send you a few to try via options>corboard>appearance, colors custom background.

I forgot I posted this. It was solved later that day. My answer was pretty much the same as yours: 1400x1000(ish) I have to try a few to find one that works, but it got much easier. Thank you for the offer to send pics. I actually never considered intentionally tiling it.