you need something rustic then lets see.....

What about a beautiful patchwork quilt

When you say bedding, what do you mean? A mattress that will work on a rope bed? That will have to be custom made to your specifications. It will be thin and much more flexible than a conventional mattress. Or do you mean a comforter, or a duvet cover, or a bedspread? How about a hand made log cabin patterned quilt?

I am told that a futon mattress will fit perfectly. I am not sure of comfort. I have never had a futon, so...but need ideas about coverings. Bed is in restored log cabin, very authentic, not "prettied up" at all.

I used a futon mattress on an old bed and it was like a rock. It was ok for an occasional young grandkid, but I wouldn't subject an adult to it. So it depends...if someone will actually be using the bed nightly, I would do something else.

Futons are very hard. They are not comfortable for many adults. What are the measurements?

52x69 3/4

That's a custom size. You could have a foam mattress cut to size.